ORCID Profile
0000-0002-2050-8026
Current Organisation
University of Tasmania
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Research Topics
In Research Link Australia (RLA), "Research Topics" refer to ANZSRC FOR and SEO codes. These topics are either sourced from ANZSRC FOR and SEO codes listed in researchers' related grants or generated by a large language model (LLM) based on their publications.
Top 5 Research Topics
ANZSRC Field of Research (FoR)
Evolutionary Biology | Ecology And Evolution Not Elsewhere Classified | Life Histories (Incl. Population Ecology) | Population And Ecological Genetics | Sociobiology And Behavioural Ecology | Behavioural Ecology | Ecology | Genetics | Life Histories | Ecological Physiology | Environmental Science and Management | Evolutionary Biology not elsewhere classified | Genetics not elsewhere classified | Developmental Genetics (incl. Sex Determination) | Terrestrial Ecology | Animal Physiological Ecology | Ecological Impacts of Climate Change | Genetic Immunology | Comparative Physiology | Conservation And Biodiversity | Biological Adaptation
ANZSRC Socio-Economic Objective (SEO)
Biological sciences | Expanding Knowledge in the Biological Sciences | Living resources (flora and fauna) | Effects of Climate Change and Variability on Australia (excl. Social Impacts) | Mountain and High Country Flora, Fauna and Biodiversity | Ecosystem Adaptation to Climate Change | Living resources (flora and fauna) | Higher education | Climate variability | Climate change | Living resources (flora and fauna) | Expanding Knowledge in the Agricultural and Veterinary Sciences | Flora, Fauna and Biodiversity at Regional or Larger Scales |
Related Links
Publications
Mate familiarity and social learning in a monogamous lizard
Publisher: Springer Science and Business Media LLC
Date: 08-05-2018
DOI: 10.1007/S00442-018-4153-Z
Abstract: Social learning is thought to be advantageous as it allows an animal to gather information quickly without engaging in costly trial-and-error learning. However, animals should be selective about when and whom they learn from. Familiarity is predicted to positively influence an animal's reliance on social learning yet, few studies have empirically tested this theory. We used a lizard (Liopholis whitii) that forms long-term monogamous pair bonds to examine the effects of partner familiarity on social learning in two novel foraging tasks, an association and a reversal task. We allowed female lizards to observe trained conspecifics that were either familiar (social mate) or unfamiliar execute these tasks and compared these two groups with control females that did not receive social information. Lizards preferentially relied on trial-and-error learning in the association task. In the reversal task, lizards that were demonstrated by familiar partners learnt in fewer trials compared to control lizards and made more correct choices. Our results provide some evidence for context-dependent learning with lizards differentiating between when they utilize social learning, and, to a limited degree, whom they learnt from. Understanding the role of the social context in which learning occurs provides important insights into the benefits of social learning and sociality more generally.
Evolutionary ecology of telomeres: a review
Publisher: Wiley
Date: 06-10-2017
DOI: 10.1111/NYAS.13443
Abstract: Telomere-induced selection could take place if telomere-associated disease risk shortens reproductive life span and differently reduces relative fitness among in iduals. Some of these diseases first appear before reproductive senescence and could thus influence ongoing selection. We ask whether we can estimate the components of the breeder's equation for telomeres, in which the response to selection (R, by definition "evolution") is the product of ongoing selection (S) and heritability (h
Selection and constraints on offspring size-number trade-offs in sand lizards (Lacerta agilis)
Publisher: Wiley
Date: 26-02-2016
DOI: 10.1111/JEB.12838
Abstract: The trade-off between offspring size and number is a central component of life-history theory, postulating that larger investment into offspring size inevitably decreases offspring number. This trade-off is generally discussed in terms of genetic, physiological or morphological constraints however, as among-in idual differences can mask in idual trade-offs, the underlying mechanisms may be difficult to reveal. In this study, we use multivariate analyses to investigate whether there is a trade-off between offspring size and number in a population of sand lizards by separating among- and within-in idual patterns using a 15-year data set collected in the wild. We also explore the ecological and evolutionary causes and consequences of this trade-off by investigating how a female's resource (condition)- vs. age-related size (snout-vent length) influences her investment into offspring size vs. number (OSN), whether these traits are heritable and under selection and whether the OSN trade-off has a genetic component. We found a negative correlation between offspring size and number within in idual females and physical constraints (size of body cavity) appear to limit the number of eggs that a female can produce. This suggests that the OSN trade-off occurs due to resource constraints as a female continues to grow throughout life and, thus, produces larger clutches. In contrast to the assumptions of classic OSN theory, we did not detect selection on offspring size however, there was directional selection for larger clutch sizes. The repeatabilities of both offspring size and number were low and we did not detect any additive genetic variance in either trait. This could be due to strong selection (past or current) on these life-history traits, or to insufficient statistical power to detect significant additive genetic effects. Overall, the findings of this study are an important illustration of how analyses of within-in idual patterns can reveal trade-offs and their underlying causes, with potential evolutionary and ecological consequences that are otherwise hidden by among-in idual variation.
Contrasting seasonal patterns of telomere dynamics in response to environmental conditions in the ectothermic sand lizard, Lacerta agilis
Publisher: Springer Science and Business Media LLC
Date: 13-01-2020
DOI: 10.1038/S41598-019-57084-5
Abstract: Telomeres, the protective, terminal parts of the chromosomes erode during cell ision and as a result of oxidative damage by reactive oxygen species (ROS). Ectotherms rely on the ambient temperature for maintaining temperature-dependent metabolic rate, regulated through behavioural thermoregulation. Their temperature-dependant metabolism, hence also the ROS production, is indirectly regulated through thermoregulation. Consequently, a potential causal chain affecting telomere length and attrition is: temperature (in particular, its deviation from a species-specific optimum) – metabolism - ROS production – anti-oxidation - telomere erosion. We measured telomere length in sand lizards ( Lacerta agilis ) using qPCR on blood s les from 1998–2006. Effects of climatological parameters (mean temperature and average sunshine hours) in the summer and winter preceding telomere s ling were used as predictors of telomere length in mixed model analysis. During the lizards’ active period (summer), there was a largely negative effect of mean temperature and sun on telomere length, whereas a combined measure of age and size (head length) was positively related to telomere length. During the inactive period of lizards (winter), the results were largely the opposite with a positive relationship between temperature and sunshine hours and telomere length. In all four cases, thermal and age effects on telomere length appeared to be non-linear in the two sexes and seasons, with complex response surface effects on telomere length from combined age and thermal effects.
Embryonic gonadal and sexual organ development in a small viviparous skink,Niveoscincus ocellatus
Publisher: Wiley
Date: 2005
DOI: 10.1002/JEZ.A.249
Abstract: The majority of research into the timing of gonad differentiation (and sex determination) in reptiles has focused on oviparous species. This is largely because: (1) most reptiles are oviparous (2) it is easier to manipulate embryonic developmental conditions (e.g., temperature) of eggs than oviductal embryos and (3) modes of sex determination in oviparous taxa were thought to be more erse since viviparity and environmental sex determination (ESD)/temperature-dependent sex determination (TSD) were considered incompatible. However, recent evidence suggests the two may well be compatible biological attributes, opening potential new lines of enquiry into the evolution and maintenance of sex determination. Unfortunately, the baseline information on embryonic development in viviparous species is lacking and information on gonad differentiation and sexual organ development is almost non-existent. Here we present an embryonic morphological development table (10 stages), the sequence of gonad differentiation and sexual organ development for the viviparous spotted snow skink (Niveoscincus ocellatus). Gonad differentiation in this species is similar to other reptilian species. Initially, the gonads are indifferent and both male and female accessory ducts are present. During stage 2, in the middle third of development, differentiation begins as the inner medulla regresses and the cortex thickens signaling ovary development, while the opposite occurs in testis formation. At this point, the Müllerian (female reproductive) duct regresses in males until it is lost (stage 6), while females retain both ducts until after birth. In the later stages of testis development, interstitial tissue forms in the medulla corresponding to maximum development of the hemipenes in males and the corresponding regression in the females.
UV-deprived coloration reduces success in mate acquisition in male sand lizards (Lacerta agilis)
Publisher: Public Library of Science (PLoS)
Date: 13-05-2011
Of telomeres and temperature: Measuring thermal effects on telomeres in ectothermic animals
Publisher: Wiley
Date: 06-09-2022
DOI: 10.1111/MEC.16154
Abstract: Ectotherms are classic models for understanding life‐history tradeoffs, including the reproduction–somatic maintenance tradeoffs that may be reflected in telomere length and their dynamics. Importantly, life‐history traits of ectotherms are tightly linked to their thermal environment, with erse or synergistic mechanistic explanations underpinning the variation. Telomere dynamics potentially provide a mechanistic link that can be used to monitor thermal effects on in iduals in response to climatic perturbations. Growth rate, age and developmental stage are all affected by temperature, which interacts with telomere dynamics in complex and intriguing ways. The physiological processes underpinning telomere dynamics can be visualized and understood using thermal performance curves (TPCs). TPCs reflect the evolutionary history and the thermal environment during an in idual's ontogeny. Telomere maintenance should be enhanced at or near the thermal performance optimum of a species, population and in idual. The thermal sensitivity of telomere dynamics should reflect the interacting TPCs of the processes underlying them. The key processes directly underpinning telomere dynamics are mitochondrial function (reactive oxygen production), antioxidant activity, telomerase activity and telomere endcap protein status. We argue that identifying TPCs for these processes will significantly help design robust, repeatable experiments and field studies of telomere dynamics in ectotherms. Conceptually, TPCs are a valuable framework to predict and interpret taxon‐ and population‐specific telomere dynamics across thermal regimes. The literature of thermal effects on telomeres in ectotherms is sparse and mostly limited to vertebrates, but our conclusions and recommendations are relevant across ectothermic animals.
Plasticity of thermoregulatory behaviour in response to the thermal environment by widespread and alpine reptile species
Publisher: Elsevier BV
Date: 10-2017
Climate and sex ratio variation in a viviparous lizard
Publisher: The Royal Society
Date: 05-2017
Abstract: The extent to which key biological processes, such as sex determination, respond to environmental fluctuations is fundamental for assessing species' susceptibility to ongoing climate change. Few studies, however, address how climate affects offspring sex in the wild. We monitored two climatically distinct populations of the viviparous skink Niveoscincus ocellatus for 16 years, recording environmental temperatures, offspring sex and date of birth. We found strong population-specific effects of temperature on offspring sex, with female offspring more common in warm years at the lowland site but no effect at the highland site. In contrast, date of birth advanced similarly in response to temperature at both sites. These results suggest strong population-specific effects of temperature on offspring sex that are independent of climatic effects on other physiological processes. These results have significant implications for our understanding of the ecological and evolutionary consequences of variation in sex ratios under climate change.
Are increased concentrations of maternal corticosterone adaptive to offspring? A test using a placentotrophic lizard
Publisher: Wiley
Date: 26-02-2010
Examining the Role of Testosterone in Mediating Short-Term Aggressive Responses to Social Stimuli in a Lizard
Publisher: Public Library of Science (PLoS)
Date: 23-04-2015
Resource distribution mediates social and mating behavior in a family living lizard
Publisher: Oxford University Press (OUP)
Date: 19-09-2016
Males with high genetic similarity to females sire more offspring in sperm competition in Peron's tree frog Litoria peronii
Publisher: The Royal Society
Date: 29-01-2008
Abstract: Recent work has confirmed that genetic compatibility among mates can be an important determinant of siring success in sperm competition experiments and in free-ranging populations. Most of this work points towards mate choice of less related mates. However, there may also be the potential for mate choice for intermediate or even genetically similar mates to prevent outbreeding depression or hybridization with closely related taxa. We studied relatedness effects on post-copulatory gametic choice and/or sperm competition in an external fertilizer, Peron's tree frog ( Litoria peronii ), since external fertilizers offer exceptional control in order to test gametic interaction effects on probability of paternity and zygote viability. Sperm competition experiments were done blindly with respect to genetic relatedness among males and females. Thereafter, paternity of offspring was assigned using eight microsatellite loci. Three hybridization trials between L. peronii and a closely related sympatric species Litoria tyleri were also carried out. In the sperm competition trials, males that are more genetically similar to the female achieved higher siring success compared with less genetically similar males. The hybridization trials confirmed that the two species can interbreed and we suggest that the risk of hybridization may contribute to selection benefits for genetically more similar males at fertilization. To our knowledge, this study is the first to show evidence for post-copulatory selection of sperm from genetically more similar in iduals within a natural population.
Proximate determinants of telomere length in sand lizards (Lacerta agilis)
Publisher: The Royal Society
Date: 31-03-2010
Abstract: Telomeres are repeat sequences of non-coding DNA that cap the ends of chromosomes and contribute to their stability and the genomic integrity of cells. In evolutionary ecology, the main research target regarding these genomic structures has been their role in ageing and as a potential index of age. However, research on humans shows that a number of traits contribute to among-in idual differences in telomere length, in particular traits enhancing cell ision and genetic erosion, such as levels of free radicals and stress. In lizards, tail loss owing to predation attempts results in a stress-induced shift to a more cryptic lifestyle. In sand lizard ( Lacerta agilis ) males, telomere length was compromised by tail regrowth in a body size-related manner, so that small males, which already exhibit more cryptic mating tactics, were less affected than larger males. Tail regrowth just fell short of having a significant relationship with telomere length in females, and so did age in males. In females, there was a significant positive relationship between age and telomere length. We conclude that the proximate effect of compromised antipredation and its associated stress seems to have a more pronounced effect in males than in females and that age-associated telomere dynamics differ between the sexes.
Effects of variation in maternal carotenoid intake during gestation on offspring innate immune response in a matrotrophic viviparous reptile
Publisher: Wiley
Date: 04-08-2011
DOES MATE GUARDING PREVENT RIVAL MATING IN SNOW SKINKS? A TEST USING AFLP
Publisher: Herpetologists League
Date: 12-2005
DOI: 10.1655/04-85.1
Pleistocene divergence in the absence of gene flow among populations of a viviparous reptile with intraspecific variation in sex determination
Publisher: Wiley
Date: 25-03-2021
DOI: 10.1002/ECE3.7458
Abstract: Polymorphisms can lead to genetic isolation if there is differential mating success among conspecifics ergent for a trait. Polymorphism for sex‐determining system may fall into this category, given strong selection for the production of viable males and females and the low success of heterogametic hybrids when sex chromosomes differ (Haldane's rule). Here we investigated whether populations exhibiting polymorphism for sex determination are genetically isolated, using the viviparous snow skink Carinascincus ocellatus . While a comparatively high elevation population has genotypic sex determination, in a lower elevation population there is an additional temperature component to sex determination. Based on 11,107 SNP markers, these populations appear genetically isolated. “Isolation with Migration” analysis also suggests these populations erged in the absence of gene flow, across a period encompassing multiple Pleistocene glaciations and likely greater geographic proximity of populations. However, further experiments are required to establish whether genetic isolation may be a cause or consequence of differences in sex determination. Given the influence of temperature on sex in one lineage, we also discuss the implications for the persistence of this polymorphism under climate change.
MHC, health, color, and reproductive success in sand lizards
Publisher: Springer Science and Business Media LLC
Date: 09-03-2005
Evolution of maternal effects: past and present
Publisher: The Royal Society
Date: 12-03-2009
Asynchronous Male and Female Gonadal Cycles and Plasma Steroid Concentrations in a Viviparous Lizard,Niveoscincus ocellatus(Scincidae), from Tasmania
Publisher: Elsevier BV
Date: 11-1997
Abstract: The reproductive cycle in males of the skink, Niveoscincus ocellatus, is characterised by testicular development during summer, followed by mating in autumn. Plasma testosterone concentrations show a bimodal seasonal cycle, with the major peak (18.6 +/- 1.2 ng/ml) in late summer/autumn and a minor peak (7.4 +/- 1.0 ng/ml) at spring emergence. In contrast to the males, the females have a gonadal cycle in which mating is temporally dissociated from peak development of the gonads: ovulation occurs in spring and the young are born in summer. Fresh mating marks on females in spring indicate that at least part of the population mates for a second time after spring emergence. In females, plasma estradiol concentrations are significantly elevated (956 +/- 214 pg/ml) through vitellogenesis and are highest (1241 +/- 175 pg/ml) during the preovulatory phase. Plasma progesterone concentrations rise during gestation to 6.5 +/- 1.5 ng/ml, but fall in the final stage of gestation to 1.6 +/- 0.2 ng/ml. There is minimal atresia of vitellogenic follicles, suggesting that clutch size is determined when the follicles are recruited for vitellogenesis.
Costs of reproduction in a lizard species: a comparison of observational and experimental data
Publisher: Wiley
Date: 04-2001
Are behavioral syndromes invariant? Spatiotemporal variation in shy/bold behavior in squid
Publisher: Springer Science and Business Media LLC
Date: 10-12-2009
Male and female effects on fertilization success and offspring viability in the Peron's tree frog, Litoria peronii
Publisher: Wiley
Date: 10-04-2008
Geographic and Annual Variation in Life-History Traits in a Temperate Zone Australian Skink
Publisher: JSTOR
Date: 06-2001
DOI: 10.2307/1566108
IN HOT PURSUIT: FLUCTUATING MATING SYSTEM AND SEXUAL SELECTION IN SAND LIZARDS
Publisher: Wiley
Date: 05-11-2010
DOI: 10.1111/J.1558-5646.2010.01152.X
Abstract: A changing climate is expected to have profound effects on many aspects of ectotherm biology. We report on a decade-long study of free-ranging sand lizards (Lacerta agilis), exposed to an increasing mean mating season temperature and with known operational sex ratios. We assessed year-to-year variation in sexual selection on body size and postcopulatory sperm competition and cryptic female choice. Higher temperature was not linked to strength of sexual selection on body mass, but operational sex ratio (more males) did increase the strength of sexual selection on body size. Elevated temperature increased mating rate and number of sires per clutch with positive effects on offspring fitness. In years when the "quality" of a female's partners was more variable (in standard errors of a male sexual ornament), clutches showed less multiple paternity. This agrees with prior laboratory trials in which females exercised stronger cryptic female choice when male quality varied more. An increased number of sires contributing to within-clutch paternity decreased the risk of having malformed offspring. Ultimately, such variation may contribute to highly dynamic and shifting selection mosaics in the wild, with potential implications for the evolutionary ecology of mating systems and population responses to rapidly changing environmental conditions.
Gestational experience alters sex allocation in the subsequent generation
Publisher: The Royal Society
Date: 07-2016
DOI: 10.1098/RSOS.160210
Abstract: Empirical tests of adaptive maternal sex allocation hypotheses have presented inconsistent results in mammals. The possibility that mothers are constrained in their ability to adjust sex ratios could explain some of the remaining variation. Maternal effects, the influence of the maternal phenotype or genotype on her developing offspring, may constrain sex allocation through physiological changes in response to the gestational environment. We tested if maternal effects constrain future parental sex allocation through a lowered gestational stress environment in laboratory mice. Females that experienced lowered stress as embryos in utero gave birth to female-biased litters as adults, with no change to litter size. Changes in offspring sex ratio was linked to peri-conceptual glucose, as those females that had increasing blood glucose peri-conceptionally gave birth to litters with a higher male to female sex ratio. There was, however, no effect of the lowered prenatal stress for developing male embryos and their sperm sex ratio when adult. We discuss the implications of maternal effects and maternal stress environment on the lifelong physiology of the offspring, particularly as a constraint on later maternal sex allocation.
The role of size and aggression in intrasexual male competition in a social lizard species, Egernia whitii
Publisher: Springer Science and Business Media LLC
Date: 10-10-2012
Reptiles on the brink: identifying the Australian terrestrial snake and lizard species most at risk of extinction
Publisher: CSIRO Publishing
Date: 2021
DOI: 10.1071/PC20033
Abstract: Australia hosts approximately 10% of the world’s reptile species, the largest number of any country. Despite this and evidence of widespread decline, the first comprehensive assessment of the conservation status of Australian terrestrial squamates (snakes and lizards) was undertaken only recently. Here we apply structured expert elicitation to the 60 species assessed to be in the highest IUCN threat categories to estimate their probability of extinction by 2040. We also assessed the probability of successful reintroduction for two Extinct in the Wild (EW) Christmas Island species with trial reintroductions underway. Collation and analysis of expert opinion indicated that six species are at high risk (& %) of becoming extinct within the next 20 years, and up to 11 species could be lost within this timeframe unless management improves. The consensus among experts was that neither of the EW species were likely to persist outside of small fenced areas without a significant increase in resources for intense threat management. The 20 most imperilled species are all restricted in range, with three occurring only on islands. The others are endemic to a single state, with 55% occurring in Queensland. Invasive species (notably weeds and introduced predators) were the most prevalent threats, followed by agriculture, natural system modifications (primarily fire) and climate change. Increased resourcing and management intervention are urgently needed to avert the impending extinction of Australia’s imperilled terrestrial reptiles.
Diversity of reptile sex chromosome evolution revealed by cytogenetic and linked-read sequencing
Publisher: Zoological Research
Date: 2022
Offspring performance and the adaptive benefits of prolonged pregnancy: experimental tests in a viviparous lizard
Publisher: Wiley
Date: 29-06-2009
Know thy enemy: Behavioural response of a native mammal (Rattus lutreolus velutinus) to predators of different coexistence histories
Publisher: Wiley
Date: 08-10-2008
Effects of basking opportunity on birthing asynchrony in a viviparous lizard
Publisher: Elsevier BV
Date: 06-2009
Major histocompatibility complex and mate choice in sand lizards
Publisher: The Royal Society
Date: 07-11-2003
Oxidative stress physiology in relation to life history traits of a free‐living vertebrate: the spotted snow skink, Niveoscincus ocellatus
Publisher: Wiley
Date: 06-2011
DOI: 10.1111/J.1749-4877.2011.00237.X
Abstract: Recent research suggests that oxidative stress, via its links to metabolism and senescence, is a key mechanism linking life history traits such as fecundity and growth with survival however, this has rarely been put under empirical scrutiny within free-living populations. Using a wild population of live-bearing skinks, we explored how plasma antioxidant activity (OXY), reactive oxidative metabolites (ROM), and the estimated oxidative stress index are associated with female and male life history. We found that male skinks have a significantly higher ROM and estimated oxidative stress index than female skinks, but this was not accompanied by a sex difference in mortality. Both sexes showed a non-linear association between OXY and age, indicating that the oldest and youngest in iduals had the lowest OXY. Interestingly, female skinks with high OXY showed a decreased probability of survival to the following season. However, we found no significant associations between female reproductive investment (litter size or litter mass) or parturition date (i.e. metabolism) and oxidative status. Combined, our results offer mixed support for a role of oxidative stress in mediating life history traits and suggest that future studies need to explore oxidative stress during vitellogenesis in addition to using an intra-in idual approach to understand the cost of reproduction and patterns of aging.
Climate effects on offspring sex ratio in a viviparous lizard
Publisher: Wiley
Date: 11-12-2009
DOI: 10.1111/J.1365-2656.2008.01470.X
Abstract: 1. Understanding in idual and population responses to climate change is emerging as an important challenge. Because many phenotypic traits are sensitive to environmental conditions, directional climate change could significantly alter trait distribution within populations and may generate an evolutionary response. 2. In species with environment-dependent sex determination, climate change may lead to skewed sex ratios at hatching or birth. However, there are virtually no empirical data on the putative link between climatic parameters and sex ratios from natural populations. 3. We monitored a natural population of viviparous lizards with temperature-dependent sex determination (Niveoscincus ocellatus) over seven field seasons. Sex ratios at birth fluctuated significantly among years and closely tracked thermal conditions in the field, with the proportion of male offspring increasing in colder years. 4. This is the first study to demonstrate the effect of local climatic conditions (e.g. temperature) on offspring sex ratio fluctuations in a free-living population of a viviparous ectotherm. A succession of warmer-than-usual years (as predicted under many climate-change scenarios) likely would generate female-biased sex ratios at birth, while an increase in interannual variation (as also predicted under climate change scenarios) could lead to significant fluctuations in cohort sex ratios. If cohort sex ratio bias at birth leads to adult sex ratio bias, long-term directional changes in thermal conditions may have important effects on population dynamics in this species.
Disentangling the complexities of vertebrate sex allocation: a role for squamate reptiles?
Publisher: Wiley
Date: 06-2007
Structural Sequencing of Oligopeptides Aided by
Publisher: American Chemical Society (ACS)
Date: 16-10-2017
DOI: 10.1021/ACS.JNATPROD.7B00207
Abstract: This report describes an approach using
Maternal effects impact decision-making in a viviparous lizard
Publisher: The Royal Society
Date: 04-2018
Abstract: Stressful conditions experienced during early development can have deleterious effects on offspring morphology, physiology and behaviour. However, few studies have examined how developmental stress influences an in idual's cognitive phenotype. Using a viviparous lizard, we show that the availability of food resources to a mother during gestation influences a key component of her offspring's cognitive phenotype: their decision-making. Offspring from females who experienced low resource availability during gestation did better in an anti-predatory task that relied on spatial associations to guide their decisions, whereas offspring from females who experienced high resource availability during gestation did better in a foraging task that relied on colour associations to inform their decisions. This shows that the prenatal environment can influence decision-making in animals, a cognitive trait with functional implications later in life.
Testing the quality of a carrier: a field experiment on lizard signalers
Publisher: Wiley
Date: 03-2009
DOI: 10.1111/J.1558-5646.2008.00569.X
Abstract: In the Australian painted dragon lizard (Ctenophorus pictus), males occur in two different morphs with respect to gular color, with or without a yellow bib. Males without a bib lost within-clutch paternity significantly more often to rivals than bibbed males. Thus, it appears that bibs identify some phenotypic advantage linked to competitive ability. To test whether this could be related to whole-organism capacity to withstand an increased workload (due to better health and vigor, or evolved differences in self-maintenance), we implanted males with a lead pellet (loaded), Styrofoam pellet (controls), or sham-operated males without implants (shams), and compared male categories with respect to how they maintained body mass during the mating season. Somewhat unexpectedly, bibbed males consistently lost more body weight across all treatments and controls, although we could not verify that this translated into higher mortality in this short-lived animal (about 80% survive for one year only). However, bibbed males may invest more into "mating success" than nonbibbed males, which agrees with our experimental results and paternity data.
Behavioural syndromes and structural and temporal consistency of behavioural traits in a social lizard
Publisher: Wiley
Date: 29-01-2015
DOI: 10.1111/JZO.12217
In utero exposure to the oestrogen mimic diethylstilbestrol disrupts gonadal development in a viviparous reptile
Publisher: CSIRO Publishing
Date: 2015
DOI: 10.1071/RD13411
Abstract: The ubiquitous presence of endocrine-disrupting chemicals (EDCs) in the environment is of major concern. Studies on oviparous reptiles have significantly advanced knowledge in this field however, 30% of reptilian species are viviparous (live-bearing), a parity mode in which both yolk and a placenta support embryonic development, thus exposure to EDCs may occur via multiple routes. In this first study of endocrine disruption in a viviparous lizard (Niveoscincus metallicus), we aimed to identify effects of the oestrogen mimic diethylstilbestrol (DES) on gonadal development. At the initiation of sexual differentiation, pregnant N. metallicus were treated with a single dose of DES at 100 or 10 µg kg–1, a vehicle solvent or received no treatment. There was no dose-response effect, but the testes of male neonates born to DES-exposed mothers showed reduced organisation of seminiferous tubules and a lack of germ cells compared with those from control groups. The ovaries of female neonates born to DES-exposed mothers exhibited phenotypic abnormalities of ovarian structure, oocytes and follicles compared with controls. The results indicate that, in viviparous lizards, maternal exposure to oestrogenic EDCs during gestation may have profound consequences for offspring reproductive fitness.
Within‐population variation in social strategies characterize the social and mating system of an Australian lizard, Egernia whitii
Publisher: Wiley
Date: 19-11-2009
Geographic and taxonomic patterns of extinction risk in Australian squamates
Publisher: Elsevier BV
Date: 10-2019
Placental and embryonic tissues exhibit aromatase activity in the viviparous lizard Niveoscincus metallicus
Publisher: Elsevier BV
Date: 05-2014
DOI: 10.1016/J.YGCEN.2014.02.020
Abstract: Aromatase is a key regulator of circulating testosterone (T) and 17-β-oestradiol (E2), two steroids which are critical to the development, maintenance and function of reproductive tissues. The role of aromatase in sexual differentiation in oviparous (egg-laying) reptiles is well understood, yet has never been explored in viviparous (live-bearing) reptiles. As a first step towards understanding the functions of aromatase during gestation in viviparous reptiles, we measured aromatase activity in maternal and embryonic tissues at three stages of gestation in the viviparous skink, Niveoscincus metallicus. Maternal ovaries and adrenals maintained high aromatase activity throughout gestation. During the early phases of embryonic development, placental aromatase activity was comparable to that in maternal ovaries, but declined significantly at progressive stages of gestation. Aromatase activity in the developing brains and gonads of embryos was comparable with measurements in oviparous reptiles. Aromatase activity in the developing brains peaked mid development, and declined to low levels in late stage embryos. Aromatase activity in the embryonic gonads was low at embryonic stage 29-34, but increased significantly at mid-development and then remained high in late stage embryos. We conclude that ovarian estrogen synthesis is supplemented by placental aromatase activity and that maternal adrenals provide an auxiliary source of sex steroid. The pattern of change in aromatase activity in embryonic brains and gonads suggests that brain aromatase is important during sexual differentiation, and that embryonic gonads are increasingly steroidogenic as development progresses. Our data indicate vital roles of aromatase in gestation and development in viviparous lizards.
Temperature and telomeres: thermal treatment influences telomere dynamics through a complex interplay of cellular processes in a cold-climate skink
Publisher: Springer Science and Business Media LLC
Date: 16-10-2019
DOI: 10.1007/S00442-019-04530-W
Abstract: Telomere dynamics vary fundamentally between endothermic populations and species as a result of differences in life history, yet we know little about these patterns in ectotherms. In ectotherms, the relationships between climate, metabolism and life history suggest that telomere attrition should be higher at relatively high environmental temperatures compared to relatively low environmental temperatures, but these effects may vary between populations due to local adaptation. To address this hypothesis, we s led reactive oxygen species (ROS) and telomere length of lizards from warm lowland and cool highland populations of a climatically widespread lizard species that we exposed to hot or cold basking treatments. The hot treatment increased relative telomere length compared to the cold treatment independent of climatic origin or ROS levels. Lizards from the cool highland region had lower ROS levels than those from the warm lowland region. Within the highland lizards, ROS increased more in the cold basking treatment than the hot basking treatment. These results are in the opposite direction to those predicted, suggesting that the relationships between temperature, metabolism, ROS and telomere dynamics are not straightforward. Future work incorporating detailed understanding of the thermal reaction norms of these and other linked traits is needed to fully understand these processes.
Thermal Plasticity in Behavioral Traits Mediates Mating and Reproductive Dynamics in an Ectotherm
Publisher: University of Chicago Press
Date: 06-2023
DOI: 10.1086/724381
The role of Haldane's rule in sex allocation
Publisher: Wiley
Date: 2005
The evolution of sex ratios and sex-determining systems
Publisher: Elsevier BV
Date: 06-2007
DOI: 10.1016/J.TREE.2007.03.008
Abstract: Sex determination is a fundamental process governed by erse mechanisms. Sex ratio selection is commonly implicated in the evolution of sex-determining systems, although formal models are rare. Here, we argue that, although sex ratio selection can induce shifts in sex determination, genomic conflicts between parents and offspring can explain why single-factor systems (e.g. XY/XX or ZW/ZZ) are common even in species that experience selection for biased sex ratios. Importantly, evolutionary shifts in sex determination do not always result in the biased production of sons and daughters sensu sex ratio theory. Thus, equal sex ratios might be an emergent character of sex-determining systems even when biased sex ratios are favored by selection.
Geographic Variation in Age and Size at Maturity in a Small Australian Viviparous Skink
Publisher: American Society of Ichthyologists and Herpetologists (ASIH)
Date: 08-2001
Promiscuity resolves constraints on social mate choice imposed by population viscosity
Publisher: Wiley
Date: 22-01-2014
DOI: 10.1111/MEC.12618
Abstract: Population viscosity can have major consequences for adaptive evolution, in particular for phenotypes involved in social interactions. For ex le, population viscosity increases the probability of mating with close kin, resulting in selection for mechanisms that circumvent the potential negative consequences of inbreeding. Female promiscuity is often suggested to be one such mechanism. However, whether avoidance of genetically similar partners is a major selective force shaping patterns of promiscuity remains poorly supported by empirical data. Here, we show (i) that fine-scale genetic structure constrains social mate choice in a pair-bonding lizard, resulting in in iduals pairing with genetically similar in iduals, (ii) that these constraints are circumvented by multiple mating with less related in iduals and (iii) that this results in increased heterozygosity of offspring. Despite this, we did not detect any significant effects of heterozygosity on offspring or adult fitness or a strong relationship between pair relatedness and female multiple mating. We discuss these results within the context of incorporating the genetic context dependence of mating strategies into a holistic understanding of mating system evolution.
Antarctic sea anemone distribution, abundance and relationships with habitat composition, community structure and anthropogenic disturbance
Publisher: Cambridge University Press (CUP)
Date: 13-02-2020
DOI: 10.1017/S0954102019000567
Abstract: Understanding the distribution, abundance and habitat preferences of species in the Southern Ocean provides a foundation for assessing the impacts of environmental change and anthropogenic disturbance on Antarctic ecosystems. In near-shore waters at Casey and Davis Stations, photoquadrat surveys were used to determine sea anemone distribution and abundance, habitat preferences, associations with other species and the impact of human disturbance on sea anemone distribution. Two distinct sea anemone morphotypes were found in this study: large sea anemones that require hard substrate for attachment and small, burrowing sea anemones found in muddy sediment. The large sea anemones were found in rocky habitats, with the exception of some sedimentary habitats where other biota were used as substrate. The large sea anemones were associated with a erse community of epibenthic species found in rocky habitats. The burrowing sea anemones were associated with a less erse assemblage of sediment-dwelling epibenthos. At Casey Station, sea anemones were more abundant in habitats adjacent to a former waste disposal site than at control sites. The reason for this is not yet known, but may be due to high organic matter inputs or, alternatively, a longer sea ice duration providing protection from ice scour.
Maternal basking opportunity affects juvenile phenotype in a viviparous lizard
Publisher: Wiley
Date: 06-2000
CLIMATE CHANGE, MULTIPLE PATERNITY AND OFFSPRING SURVIVAL IN LIZARDS
Publisher: Wiley
Date: 13-07-2011
Sex Differences in Sand Lizard Telomere Inheritance: Paternal Epigenetic Effects Increases Telomere Heritability and Offspring Survival
Publisher: Public Library of Science (PLoS)
Date: 22-04-2011
ALTITUDINAL DIVERGENCE IN MATERNAL THERMOREGULATORY BEHAVIOUR MAY BE DRIVEN BY DIFFERENCES IN SELECTION ON OFFSPRING SURVIVAL IN A VIVIPAROUS LIZARD
Publisher: Wiley
Date: 19-04-2011
DOI: 10.1111/J.1558-5646.2011.01303.X
Abstract: Plastic responses to temperature during embryonic development are common in ectotherms, but their evolutionary relevance is poorly understood. Using a combination of field and laboratory approaches, we demonstrate altitudinal ergence in the strength of effects of maternal thermal opportunity on offspring birth date and body mass in a live-bearing lizard (Niveoscincus ocellatus). Poor thermal opportunity decreased birth weight at low altitudes where selection on body mass was negligible. In contrast, there was no effect of maternal thermal opportunity on body mass at high altitudes where natural selection favored heavy offspring. The weaker effect of poor maternal thermal opportunity on offspring development at high altitude was accompanied by a more active thermoregulation and higher body temperature in highland females. This may suggest that passive effects of temperature on embryonic development have resulted in evolution of adaptive behavioral compensation for poor thermal opportunity at high altitudes, but that direct effects of maternal thermal environment are maintained at low altitudes because they are not selected against. More generally, we suggest that phenotypic effects of maternal thermal opportunity or incubation temperature in reptiles will most commonly reflect weak selection for canalization or selection on maternal strategies rather than adaptive plasticity to match postnatal environments.
Maternal care in a social lizard: links between female aggression and offspring fitness
Publisher: Elsevier BV
Date: 10-2008
The diversity of population responses to environmental change
Publisher: Wiley
Date: 09-12-2018
DOI: 10.1111/ELE.13195
Effects of Maternal Basking and Food Quantity during Gestation Provide Evidence for the Selective Advantage of Matrotrophy in a Viviparous Lizard
Publisher: Public Library of Science (PLoS)
Date: 26-07-2012
Phylogeographic parallelism: Concordant patterns in closely related species illuminate underlying mechanisms in the historically glaciated Tasmanian landscape
Publisher: Wiley
Date: 16-04-2020
DOI: 10.1111/JBI.13831
Is fecundity the ultimate cause of female‐biased size dimorphism in a dragon lizard?*
Publisher: Wiley
Date: 18-09-2007
Maternal presence facilitates plasticity in offspring behavior: insights into the evolution of parental care
Publisher: Oxford University Press (OUP)
Date: 29-09-2018
Corticosterone: a costly mediator of signal honesty in sand lizards
Publisher: Wiley
Date: 28-09-2016
DOI: 10.1002/ECE3.2318
Evidence for placental transfer of maternal corticosterone in a viviparous lizard
Publisher: Elsevier BV
Date: 10-2011
DOI: 10.1016/J.CBPA.2011.05.028
Abstract: In mammals, there is experimental evidence that circulating maternal cortisol is transferred to the embryos across the placenta during gestation. Direct effects of this maternal cortisol may allow embryos to display phenotypic plasticity to cope with postnatal environments (i.e., pre-programming). The potential for maternal hormone induced-adaptation may be of considerable evolutionary significance in viviparous animals. However, to date, there is no such direct evidence that circulating maternal corticosterone passes through the placenta and into the embryos of viviparous reptiles. In this study, we assessed the transfer of (3)H-corticosterone injected into females of the lizard Pseudemoia entrecasteauxii into maternal blood, maternal liver, the embryo, the yolk and the amniotic fluid during mid-to-late gestation. We provide direct evidence that circulating maternal corticosterone passes through the placenta into the embryos in this species. Transfer of maternal corticosterone into the embryos significantly decreased at the end of embryonic development. We discuss these results in terms of the relationships between the degree of corticosterone transfer and embryonic stage. These results demonstrate the potential for direct effects of maternal corticosterone, including endocrine pre-programming, upon the developing embryos in viviparous lizards.
Habitat saturation promotes delayed dispersal in a social reptile
Publisher: Oxford University Press (OUP)
Date: 02-01-2017
Patterns in the distribution and abundance of sea anemones off Dumont d'Urville Station, Antarctica
Publisher: Springer Science and Business Media LLC
Date: 24-05-2018
Quantitative genetics of breeding coloration in sand lizards; genic capture unlikely to maintain additive genetic variance
Publisher: Springer Science and Business Media LLC
Date: 20-03-2023
DOI: 10.1038/S41437-023-00607-8
Abstract: Sexual selection on fitness-determining traits should theoretically erode genetic variance and lead to low heritability. However, many sexually selected traits maintain significant phenotypic and additive genetic variance, with explanations for this “lek paradox” including genic capture due to condition-dependence, and breaks on directional selection due to environmental sources of variance including maternal effects. Here we investigate genetic and environmental sources of variance in the intrasexually selected green badge of the sand lizard ( Lacerta agilis ). The badge functions as a cue to male fighting ability in this species, and male–male interactions determine mate acquisition. Using animal models on a pedigree including three generations of males measured over an extensive 9-year field study, we partition phenotypic variance in both badge size and body condition into additive genetic, maternal, and permanent environmental effects experienced by an in idual over its lifespan. Heritability of badge size was 0.33 with a significant estimate of underlying additive genetic variance. Body condition was strongly environmentally determined in this species and did not show either significant additive genetic variance or heritability. Neither badge size nor body condition was responsive to maternal effects. We propose that the lack of additive genetic variance and heritability of body condition makes it unlikely that genic capture mechanisms maintain additive genetic variance for badge size. That said, genic capture was originally proposed for male traits under female choice, not agonistic selection. If developmental pathways generating variance in body condition, and/or the covarying secondary sex trait, differ between inter- and intrasexual selection, or the rate at which their additive genetic variance or covariance is depleted, future work may show whether genic capture is largely restricted to intersexual selection processes.
Multi‐scale approach to understanding climate effects on offspring size at birth and date of birth in a reptile
Publisher: Wiley
Date: 06-2010
DOI: 10.1111/J.1749-4877.2010.00201.X
Abstract: Climate change is already impacting species around the world. Although most focus has been on the effect of temperature, changes in climatic variables other than temperature are also expected to drive biological change. Current models suggest that ectotherms, such as reptiles, will be strongly affected by climate change however, data from natural populations are rare. Here, we use extensive data from 2 populations of a viviparous lizard (Niveoscincus ocellatus Gray, 1845) at the climatic extreme of the species distribution. We examine the effects of climate at a local, a regional and a global scale (thus, integrating a suite of variables at different spatial and temporal scales) on 2 key life history traits: offspring date of birth and size at birth. Overall, our results show that across 9 years of study, local temperature had strong effects on the offspring date of birth but not on the size at birth. Therefore, a rapid increase in local temperature throughout the species range (as predicted under global warming scenarios) is likely to affect phenological processes with potential concomitant effects on offspring fitness and survival.
Conservation status of the world's skinks (Scincidae): Taxonomic and geographic patterns in extinction risk
Publisher: Elsevier BV
Date: 05-2021
Consistent paternity skew through ontogeny in peron's tree frog (Litoria peronii)
Publisher: Public Library of Science (PLoS)
Date: 14-12-2009
Editorial for the Michael Bull special issue
Publisher: Wiley
Date: 28-05-2020
DOI: 10.1111/AEC.12906
Birthing asynchrony is not a consequence of asynchronous offspring development in a non‐avian vertebrate, the Australian skink Egernia whitii
Publisher: Wiley
Date: 19-05-2007
Fit and fat from enlarged badges: a field experiment on male sand lizards
Publisher: The Royal Society
Date: 07-05-2004
Climate-driven population divergence in sex-determining systems
Publisher: Springer Science and Business Media LLC
Date: 27-10-2010
DOI: 10.1038/NATURE09512
Abstract: Sex determination is a fundamental biological process, yet its mechanisms are remarkably erse. In vertebrates, sex can be determined by inherited genetic factors or by the temperature experienced during embryonic development. However, the evolutionary causes of this ersity remain unknown. Here we show that live-bearing lizards at different climatic extremes of the species' distribution differ in their sex-determining mechanisms, with temperature-dependent sex determination in lowlands and genotypic sex determination in highlands. A theoretical model parameterized with field data accurately predicts this ergence in sex-determining systems and the consequence thereof for variation in cohort sex ratios among years. Furthermore, we show that ergent natural selection on sex determination across altitudes is caused by climatic effects on lizard life history and variation in the magnitude of between-year temperature fluctuations. Our results establish an adaptive explanation for intra-specific ergence in sex-determining systems driven by phenotypic plasticity and ecological selection, thereby providing a unifying framework for integrating the developmental, ecological and evolutionary basis for variation in vertebrate sex determination.
Fixed Allele Differences Associated With the Centromere Reveal Chromosome Morphology and Rearrangements in a Reptile (Varanus acanthurus BOULENGER)
Publisher: Oxford University Press (OUP)
Date: 06-2023
Abstract: Chromosome rearrangements are often implicated with genomic ergence and are proposed to be associated with species evolution. Rearrangements alter the genomic structure and interfere with homologous recombination by isolating a portion of the genome. Integration of multiplatform next-generation DNA sequencing technologies has enabled putative identification of chromosome rearrangements in many taxa however, integrating these data sets with cytogenetics is still uncommon beyond model genetic organisms. Therefore, to achieve the ultimate goal for the genomic classification of eukaryotic organisms, physical chromosome mapping remains critical. The ridge-tailed goannas (Varanus acanthurus BOULENGER) are a group of dwarf monitor lizards comprised of several species found throughout northern Australia. These lizards exhibit extreme ergence at both the genic and chromosomal levels. The chromosome polymorphisms are widespread extending across much of their distribution, raising the question if these polymorphisms are homologous within the V. acanthurus complex. We used a combined genomic and cytogenetic approach to test for homology across ergent populations with morphologically similar chromosome rearrangements. We showed that more than one chromosome pair was involved with the widespread rearrangements. This finding provides evidence to support de novo chromosome rearrangements have occurred within populations. These chromosome rearrangements are characterized by fixed allele differences originating in the vicinity of the centromeric region. We then compared this region with several other assembled genomes of reptiles, chicken, and the platypus. We demonstrated that the synteny of genes in Reptilia remains conserved despite centromere repositioning across these taxa.
Do female amphibians and reptiles have greater reproductive output if they have more mates?
Publisher: Springer Science and Business Media LLC
Date: 07-2022
DOI: 10.1007/S00265-022-03194-6
Abstract: In general, males mate with multiple females to increase in idual reproductive success. Whether or not, and under what circumstances, females benefit from multiple mating has been less clear. Our review of 154 studies covering 184 populations of hibians and reptiles showed that polyandry was widespread and variable among and within taxonomic groups. We investigated whether hibian and reptile females had greater reproductive output as the number of sires for offspring increased. Meta-analysis revealed significant heterogeneity in the dataset of all taxa. Expected heterozygosity was a significant moderator (covariate) of positive relationships between female reproductive output and the number of sires, but a sensitivity test showed the result was tenuous. Significant heterogeneity remained despite controlling for expected heterozygosity and other variables but was resolved for most taxonomic groups with subgroup meta-analyses. Subgroup meta-analyses showed that only female salamanders (Caudata) had significantly greater reproductive output with an increased number of sires. For many species of Caudata, males cannot coerce females into accepting spermatophores. We therefore suggest that if females control the number of matings, they can use polyandry to increase their fitness. Caudata offers ideal models with which to test this hypothesis and to explore factors enabling and maintaining the evolution of female choice. Outstanding problems may be addressed by expanding taxonomic coverage and data collection and improving data reporting. Many factors and combinations of factors drive polyandry. Whether or not females benefit from mating with more than one male remains equivocal. Focusing on hibians and reptiles, our analyses demonstrate that female salamanders produced more offspring when mated with multiple males, whereas this was not the case for reptiles. Unlike many other species in our dataset, the polyandrous female salamanders fully control sperm intake and have chosen to mate multiple times. We further highlight problems and key directions for future research in the field.
Individual telomere dynamics and their links to life history in a viviparous lizard
Publisher: The Royal Society
Date: 26-05-2021
Abstract: Emerging patterns suggest telomere dynamics and life history are fundamentally linked in endotherms through life-history traits that mediate the processes underlying telomere attrition. Unlike endotherms, ectotherms maintain the ability to lengthen somatic telomeres throughout life and the link between life-history strategies and ectotherm telomere dynamics is unknown. In a well-characterized model system ( Niveoscincus ocellatus ), we used long-term longitudinal data to study telomere dynamics across climatically ergent populations. We found longer telomeres in in iduals from the cool highlands than those from the warm lowlands at birth and as adults. The key determinant of adult telomere length across populations was telomere length at birth, with population-specific effects of age and growth on adult telomere length. The reproductive effort had no proximate effect on telomere length in either population. Maternal factors influenced telomere length at birth in the warm lowlands but not the cool highlands. Our results demonstrate that life-history traits can have pervasive and context-dependent effects on telomere dynamics in ectotherms both within and between populations. We argue that these telomere dynamics may reflect the populations' different life histories, with the slow-growing cool highland population investing more into telomere lengthening compared to the earlier-maturing warm lowland population.
Mating system variation and morph fluctuations in a polymorphic lizard
Publisher: Wiley
Date: 12-2007
Late stage deferral of parturition in the viviparous lizard Niveoscincus ocellatus (Gray 1845): implications for offspring quality and survival
Publisher: Oxford University Press (OUP)
Date: 21-03-2007
A Methodology to Integrate Professional Skill Development throughout an ICT Curriculum
Publisher: ACM
Date: 15-06-2020
Reproductive Correlates of Abdominal Fat Body Mass in Niveoscincus ocellatus, a Skink with an Asynchronous Reproductive Cycle
Publisher: JSTOR
Date: 09-2001
DOI: 10.2307/1565958
Characterisation and cross-amplification of sex-specific genetic markers in Australasian Egerniinae lizards and their implications for understanding the evolution of sex determination and social compl
Publisher: CSIRO Publishing
Date: 03-02-2022
DOI: 10.1071/ZO21023
Abstract: Sex is a pervasive factor that underpins functional phenotypic variation across a range of traits. Although sex can usually be distinguished morphologically, in some species this is not possible. The development of genetic markers for sex identification is, thus, key if we are to incorporate sex into an understanding of ecological or evolutionary process. Here we develop genetic markers for the identification of sex within an iconic Australian lizard group, the Egernia group, which is notable for its complex social behaviour. We used restriction-site associated DNA sequencing to characterise sex-specific genetic sequences for a key member of the group, Liopholis whitii, and designed primers for four of these putative sex-specific sequences. These primers lified across some, but not all, species of the group. Our results provided several important insights. They suggest conservatism of a XX/XY sex determination system within the group as well as sex-specific genomic regions that appear independent of the conserved genomic regions identified in other skink species. More broadly, the development of sex markers for the Egernia group opens up a range of potential research questions related to the role that sex plays in the mediation of social behaviour and, through this, the emergence and stability of social life.
An Exploratory Study of Factors Affecting Attrition within an ICT Degree
Publisher: ACM
Date: 03-02-2020
An experimental test of relatedness-based mate discrimination in a social lizard
Publisher: Springer Science and Business Media LLC
Date: 06-10-2016
Telomere length varies substantially between blood cell types in a reptile
Publisher: The Royal Society
Date: 06-2020
DOI: 10.1098/RSOS.192136
Abstract: Telomeres are repeat sequences of non-coding DNA-protein molecules that cap or intersperse metazoan chromosomes. Interest in telomeres has increased exponentially in recent years, to now include their ongoing dynamics and evolution within natural populations where in iduals vary in telomere attributes. Phylogenetic analyses show profound differences in telomere length across non-model taxa. However, telomeres may also differ in length within in iduals and between tissues. The latter becomes a potential source of error when researchers use different tissues for extracting DNA for telomere analysis and scientific inference. A commonly used tissue type for assessing telomere length is blood, a tissue that itself varies in terms of nuclear content among taxa, in particular to what degree their thrombocytes and red blood cells (RBCs) contain nuclei or not. Specifically, when RBCs lack nuclei, leucocytes become the main source of telomeric DNA. RBCs and leucocytes differ in lifespan and how long they have been exposed to ‘senescence' and erosion effects. We report on a study in which cells in whole blood from in idual Australian painted dragon lizards ( Ctenophorus pictus ) were identified using flow cytometry and their telomere length simultaneously measured. Lymphocyte telomeres were on average 270% longer than RBC telomeres, and in azurophils (a reptilian monocyte), telomeres were more than 388% longer than those in RBCs. If this variation in telomere length among different blood cell types is a widespread phenomenon, and DNA for comparative telomere analyses are sourced from whole blood, evolutionary inference of telomere traits among taxa may be seriously complicated by the blood cell type comprising the main source of DNA.
Managing consequences of climate-driven species redistribution requires integration of ecology, conservation and social science
Publisher: Wiley
Date: 06-2018
DOI: 10.1111/BRV.12344
Abstract: Climate change is driving a pervasive global redistribution of the planet's species. Species redistribution poses new questions for the study of ecosystems, conservation science and human societies that require a coordinated and integrated approach. Here we review recent progress, key gaps and strategic directions in this nascent research area, emphasising emerging themes in species redistribution biology, the importance of understanding underlying drivers and the need to anticipate novel outcomes of changes in species ranges. We highlight that species redistribution has manifest implications across multiple temporal and spatial scales and from genes to ecosystems. Understanding range shifts from ecological, physiological, genetic and biogeographical perspectives is essential for informing changing paradigms in conservation science and for designing conservation strategies that incorporate changing population connectivity and advance adaptation to climate change. Species redistributions present challenges for human well-being, environmental management and sustainable development. By synthesising recent approaches, theories and tools, our review establishes an interdisciplinary foundation for the development of future research on species redistribution. Specifically, we demonstrate how ecological, conservation and social research on species redistribution can best be achieved by working across disciplinary boundaries to develop and implement solutions to climate change challenges. Future studies should therefore integrate existing and complementary scientific frameworks while incorporating social science and human-centred approaches. Finally, we emphasise that the best science will not be useful unless more scientists engage with managers, policy makers and the public to develop responsible and socially acceptable options for the global challenges arising from species redistributions.
Persistence and dispersal in a Southern Hemisphere glaciated landscape: the phylogeography of the spotted snow skink (Niveoscincus ocellatus) in Tasmania
Publisher: Springer Science and Business Media LLC
Date: 26-06-2015
Chromosomics: Bridging the Gap between Genomes and Chromosomes
Publisher: MDPI AG
Date: 20-08-2019
Abstract: The recent advances in DNA sequencing technology are enabling a rapid increase in the number of genomes being sequenced. However, many fundamental questions in genome biology remain unanswered, because sequence data alone is unable to provide insight into how the genome is organised into chromosomes, the position and interaction of those chromosomes in the cell, and how chromosomes and their interactions with each other change in response to environmental stimuli or over time. The intimate relationship between DNA sequence and chromosome structure and function highlights the need to integrate genomic and cytogenetic data to more comprehensively understand the role genome architecture plays in genome plasticity. We propose adoption of the term ‘chromosomics’ as an approach encompassing genome sequencing, cytogenetics and cell biology, and present ex les of where chromosomics has already led to novel discoveries, such as the sex-determining gene in eutherian mammals. More importantly, we look to the future and the questions that could be answered as we enter into the chromosomics revolution, such as the role of chromosome rearrangements in speciation and the role more rapidly evolving regions of the genome, like centromeres, play in genome plasticity. However, for chromosomics to reach its full potential, we need to address several challenges, particularly the training of a new generation of cytogeneticists, and the commitment to a closer union among the research areas of genomics, cytogenetics, cell biology and bioinformatics. Overcoming these challenges will lead to ground-breaking discoveries in understanding genome evolution and function.
What are we measuring? Novices agree amongst themselves (but not always with experts) in their assessment of dog behaviour
Publisher: Wiley
Date: 15-02-2019
DOI: 10.1111/ETH.12846
Limited effects of inbreeding on breeding coloration
Publisher: Oxford University Press (OUP)
Date: 30-01-2023
Abstract: Animal color signals may function as indicators of fighting ability when males compete for access to females. This allows opponents to settle aggressive interactions before they escalate into physical combat and injury. Thus, there may be strong directional selection on these traits, towards enhanced signal quality. This renders sexually selected traits particularly susceptible to inbreeding depression, due to relatively low ratios of additive genetic variance to dominance variance. We measured the effects of inbreeding on an intrasexually selected color signal (“the badge”) in a population of Swedish sand lizards (Lacerta agilis) using the Rhh software based on 17-21 microsatellites. Males of this sexually dichromatic species use the badge during aggressive interactions to display, and assess, fighting ability. We found negative effects of homozygosity on badge size, saturation, and brightness. However, no such effects were observed on color hue. Pair-wise correlations between badge size, hue, and saturation were all statistically significant. Thus, the sand lizard ‘badge’ is a multicomponent signal with variation explained by covariation in badge size, saturation and color hue. Body mass corrected for skeletal size (“body condition”) positively predicted badge size and saturation, encouraging future research on the extent that sexual signals may convey information on multigene targets (i.e., ‘genic capture’).
Thermal biology of the spotted snow skink, Niveoscincus ocellatus, along an altitudinal gradient
Publisher: CSIRO Publishing
Date: 2019
DOI: 10.1071/ZO18014
Abstract: Body temperatures in ectotherms are strongly affected by their thermal environment. Ectotherms respond to variation in the thermal environment either by modification of behavioural thermoregulation to maintain their optimal body temperature or by shifting their optimal body temperature. In this study, the body temperatures of males of three populations of spotted snow skinks, Niveoscincus ocellatus, living along an altitudinal gradient (low, mid, and high altitude) were studied in the field and laboratory in spring, summer, and autumn, representing the full activity period of this species. The environmental variation across both sites and seasons affected their field active body temperatures. At the low and mid altitude, N. ocellatus had a higher mean body temperature than at the high altitude. Animals achieved their thermal preference at the low and mid altitude sites in all seasons. At the high altitude, however, N. ocellatus struggled to reach its preferred body temperatures, especially in autumn. The lower body temperature at the high-altitude site is likely due to limited thermal opportunity and/or an effect of avoiding the costs associated with increased intensity of basking.
Sex reversal explains some, but not all, climate-mediated sex ratio variation within a viviparous reptile
Publisher: The Royal Society
Date: 06-2022
Abstract: Evolutionary transitions in sex-determining systems have occurred frequently yet understanding how they occur remains a major challenge. In reptiles, transitions from genetic to temperature-dependent sex determination can occur if the gene products that determine sex evolve thermal sensitivity, resulting in sex-reversed in iduals. However, evidence of sex reversal is limited to oviparous reptiles. Here we used thermal experiments to test whether sex reversal is responsible for differences in sex determination in a viviparous reptile, Carinascincus ocellatus, a species with XY sex chromosomes and population-specific sex ratio response to temperature. We show that sex reversal is occurring and that its frequency is related to temperature. Sex reversal was unidirectional (phenotypic males with XX genotype) and observed in both high- and low-elevation populations. We propose that XX-biased genotypic sex ratios could produce either male- or female-biased phenotypic sex ratios as observed in low-elevation C. ocellatus under variable rates of XX sex reversal. We discuss reasons why sex reversal may not influence sex ratios at high elevation. Our results suggest that the mechanism responsible for evolutionary transitions from genotypic to temperature-dependent sex determination is more complex than can be explained by a single process such as sex reversal.
Seasonal shifts along the oviparity–viviparity continuum in a cold‐climate lizard population
Publisher: Wiley
Date: 13-11-2017
DOI: 10.1111/JEB.13202
Abstract: Squamate embryos require weeks of high temperature to complete development, with the result that cool climatic areas are dominated by viviparous taxa (in which gravid females can sun-bask to keep embryos warm) rather than oviparous taxa (which rely on warm soil to incubate their eggs). How, then, can some oviparous taxa reproduce successfully in cool climates - especially late in summer, when soil temperatures are falling? Near the northern limit of their distribution (in Sweden), sand lizards (Lacerta agilis) shift tactics seasonally, such that the eggs in late clutches complete development more quickly (when incubated at a standard temperature) than do those of early clutches. That acceleration is achieved by a reduction in egg size and by an increase in the duration of uterine retention of eggs (especially, after cool weather). Our results clarify the ability of oviparous reptiles to reproduce successfully in cool climates and suggest a novel advantage to reptilian viviparity in such conditions: by maintaining high body temperatures, viviparous females may escape the need to reduce offspring size in late-season litters.
Inconsistent inbreeding effects during lizard ontogeny
Publisher: Springer Science and Business Media LLC
Date: 05-04-2019
Potential ‘costs of reproduction’ in a skink: Inter‐ and intrapopulational variation
Publisher: Wiley
Date: 04-2001
Snow skinks (Niveoscincus ocellatus) do not shift their sex allocation patterns in response to mating history
Publisher: Brill
Date: 2009
Net superoxide levels: steeper increase with activity in cooler female and hotter male lizards
Publisher: The Company of Biologists
Date: 03-2012
DOI: 10.1242/JEB.062257
Abstract: Ectotherms increase their body temperature in response to ambient heat, thereby elevating their metabolic rate. An often inferred consequence of this is an overall upregulation of gene expression and energetic expenditure, and a concomitant increased production of reactive oxygen species (e.g. superoxide) and, perhaps, a shortened lifespan. However, recent work shows that this may be a superficial interpretation. For ex le, sometimes a reduced temperature may in fact trigger up-regulation of gene expression. We studied temperature and associated activity effects in male and female Australian painted dragon lizards (Ctenophorus pictus) by allowing the lizards to bask for 4 h versus 12 h, and scoring their associated activity (inactive versus active basking and foraging). As predicted, long-basking lizards (hereafter ‘hot’) showed heightened activity in both sexes, with a more pronounced effect in females. We then tested for sex-specific effects of basking treatment and activity levels on the increase in net levels of superoxide. In males, short-baskers (hereafter ‘cold’) had significantly more rapidly decreasing levels of superoxide per unit increasing activity than hot males. In females, however, superoxide levels increased faster with increasing activity in the cold than in the hot basking treatment, and females earlier in the ovarian cycle had lower superoxide levels than females closer to ovulation. In short, males and females differ in how their levels of reactive oxygen species change with temperature-triggered activity.
Maternal effects obscure condition-dependent sex allocation in changing environments
Publisher: The Royal Society
Date: 04-2019
DOI: 10.1098/RSOS.181885
Abstract: Climate change increases environmental fluctuations which thereby impact population demography. Species with temperature-dependent sex determination may experience more extreme sex ratio skews, but this has not been considered in species with chromosomally determined sex. However, anticipatory maternal effects cause lifelong physiological changes impacting sex ratios. Here we show, in mice, that more sons were born to mothers in good condition when their breeding environment matched their gestational environment, consistent with theoretical predictions, but mothers in mismatched environments have no condition–sex ratio relationship. Thus, the predicted effect of condition on sex ratio was obscured by maternal effects when the environment changed. This may explain extreme sex ratio skews in reintroduced or translocated populations, and sex ratio skews may become more common and less predictable with accelerating environmental change.
Atrazine disrupts gonadal development in a live-bearing lizard
Publisher: Informa UK Limited
Date: 2015
Family conflict and the evolution of sociality in reptiles
Publisher: Oxford University Press (OUP)
Date: 2009
Sperm competition and offspring viability at hybridization in Australian tree frogs, Litoria peronii and L. tyleri
Publisher: Springer Science and Business Media LLC
Date: 02-09-2010
DOI: 10.1038/HDY.2009.118
Abstract: Hybridization between closely related species often leads to reduced viability or fertility of offspring. Complete failure of hybrid offspring (post-zygotic hybrid incompatibilities) may have an important role in maintaining the integrity of reproductive barriers between closely related species. We show elsewhere that in Peron's tree frog, Litoria peronii, males more closely related to a female sire more offspring in sperm competition with a less related rival male. Observations of rare 'phenotypic intermediate' males between L. peronii and the closely related L. tyleri made us suggest that these relatedness effects on siring success may be because of selection arising from risks of costly hybridization between the two species. Here, we test this hypothesis in an extensive sperm competition experiment, which shows that there is no effect of species identity on probability of fertilization in sperm competition trials controlling for sperm concentration and sperm viability. Instead, there was a close agreement between a male's siring success in isolation with a female and his siring success with the same female in competition with a rival male regardless of species identity. Offspring viability and survival, however, were strongly influenced by species identity. Over a 14-day period, hybrid offspring suffered increasing mortality and developed more malformations and an obvious inability to swim and right themselves, leading to compromised probability of survival. Thus, hybridization in these sympatric tree frogs does not compromise fertilization but has a strong impact on offspring viability and opportunity for reinforcement selection on mate choice for conspecific partners.
Consistent male-male paternity differences across female genotypes
Publisher: The Royal Society
Date: 25-02-2009
Abstract: In a recent paper, we demonstrated that male–female genetic relatedness determines male probability of paternity in experimental sperm competition in the Peron's tree frog ( Litoria peronii ), with a more closely related male outcompeting his rival. Here, we test the hypothesis that a male–male difference in siring success with one female significantly predicts the corresponding difference in siring success with another female. With male sperm concentration held constant, and the proportion of viable sperm controlled statistically, the male–male difference in siring success with one female strongly predicted the corresponding difference in siring success with another female, and alone explained more than 62 per cent of the variance in male–male siring differences. This study demonstrates that male siring success is primarily dictated by among-male differences in innate siring success with less influence of male–female relatedness.
Sand lizard (Lacerta agilis) phenology in a warming world
Publisher: Springer Science and Business Media LLC
Date: 08-06-2013
DOI: 10.1186/S12862-015-0476-0
Abstract: Present-day climate change has altered the phenology (the timing of periodic life cycle events) of many plant and animal populations worldwide. Some of these changes have been adaptive, leading to an increase in population fitness, whereas others have been associated with fitness decline. Representing short-term responses to an altered weather regime, hitherto observed changes are largely explained by phenotypic plasticity. However, to track climatically induced shifts in optimal phenotype as climate change proceeds, evolutionary capacity in key limiting climate- and fitness-related traits is likely to be crucial. In order to produce realistic predictions about the effects of climate change on species and populations, a main target for conservation biologists is thus to assess the potential of natural populations to respond by these two mechanisms. In this study we use a large 15-year dataset on an ectotherm model, the Swedish sand lizard ( Lacerta agilis ), to investigate how higher spring temperature is likely to affect oviposition timing in a high latitude population, a trait strongly linked to offspring fitness and survival. With an interest in both the short- and potential long-term effect of rising temperatures, we applied a random regression model, which yields estimates of population-level plasticity and among-in idual variation in the average, as well as the plastic, response to temperature. Population plasticity represents capacity for short-term adjustments whereas variation among in iduals in a fitness-related trait indicates an opportunity for natural selection and hence for evolutionary adaptation. The analysis revealed both population-level plasticity and in idual-level variation in average laying date. In contrast, we found no evidence for variation among females in their plastic responses to spring temperature, which could demonstrate a similarity in responses amongst females, but may also be due to a lack of statistical power to detect such an effect. Our findings indicate that climate warming may have positive fitness effects in this lizard population through an advancement of oviposition date. This prediction is consistent over shorter and potentially also longer time scales as the analysis revealed both population-level plasticity and in idual-level variation in average laying date. However, the genetic basis for this variation would have to be examined in order to predict an evolutionary response.
Widespread chromosomal rearrangements preceded genetic divergence in a monitor lizard, Varanus acanthurus (Varanidae)
Publisher: Springer Science and Business Media LLC
Date: 06-02-2023
DOI: 10.1007/S10577-023-09715-X
Abstract: Chromosomal rearrangements are often associated with local adaptation and speciation because they suppress recombination, and as a result, rearrangements have been implicated in disrupting gene flow. Although there is strong evidence to suggest that chromosome rearrangements are a factor in genetic isolation of ergent populations, the underlying mechanism remains elusive. Here, we applied an integrative cytogenetics and genomics approach testing whether chromosomal rearrangements are the initial process, or a consequence, of population ergence in the dwarf goanna, Varanus acanthurus . Specifically, we tested whether chromosome rearrangements are indicators of genetic barriers that can be used to identify ergent populations by looking at gene flow within and between populations with rearrangements. We found that gene flow was present between in iduals with chromosome rearrangements within populations, but there was no gene flow between populations that had similar chromosome rearrangements. Moreover, we identified a correlation between reduced genetic variation in populations with a higher frequency of homozygous submetacentric in iduals. These findings suggest that chromosomal rearrangements were widespread prior to ergence, and because we found populations with higher frequencies of submetacentric chromosomes were associated with lower genetic ersity, this could indicate that polymorphisms within populations are early indicators of genetic drift.
Effects of long‐term fox baiting on species composition and abundance in an Australian lizard community
Publisher: Wiley
Date: 23-11-2005
Tail loss and telomeres: consequences of large-scale tissue regeneration in a terrestrial ectotherm
Publisher: The Royal Society
Date: 07-2019
Abstract: Large-scale tissue regeneration has potential consequences for telomere length through increases in cell ision and changes in metabolism which increase the potential for oxidative stress damage to telomeres. The effects of regeneration on telomere dynamics have been studied in fish and marine invertebrates, but the literature is scarce for terrestrial species. We experimentally induced tail autotomy in a lizard ( Niveoscincus ocellatus ) and assessed relative telomere length (RTL) in blood s les before and after partial tail regeneration while concurrently measuring reactive oxygen species (ROS) levels. The change in ROS levels was a significant explanatory variable for the change in RTL over the 60-day experiment. At the average value of ROS change, the mean RTL increased significantly in the control group (intact tails), but there was no such evidence in the regenerating group. By contrast, ROS levels decreased significantly in the regenerating group, but there was no such evidence in the control group. Combined, these results suggest that tail regeneration following autotomy involves a response to oxidative stress and this potentially comes at a cost to telomere repair. This change in telomere maintenance demonstrates a potential long-term cost of tail regeneration beyond the regrowth of tissue itself.
How accurately do behavioural observations predict reproductive success in free-ranging lizards?
Publisher: The Royal Society
Date: 02-2019
Abstract: Behavioural ecologists often use data on patterns of male–female association to infer reproductive success of free-ranging animals. For ex le, a male seen with several females during the mating season is predicted to father more offspring than a male not seen with any females. We explored the putative correlation between this behaviour and actual paternity (as revealed by microsatellite data) from a long-term study on sand lizards ( Lacerta agilis ), including behavioural observations of 574 adult males and 289 adult females, and paternity assignment of more than 2500 offspring during 1998–2007. The number of males that contributed paternity to a female's clutch was correlated with the number of males seen accompanying her in the field, but not with the number of copulation scars on her body. The number of females that a male accompanied in the field predicted the number of females with whom he fathered offspring, and his annual reproductive success (number of progeny). Although behavioural data explained less than one-third of total variance in reproductive success, our analysis supports the utility of behavioural-ecology studies for predicting paternity in free-ranging reptiles.
Potentially adaptive effects of maternal nutrition during gestation on offspring phenotype of a viviparous reptile
Publisher: The Company of Biologists
Date: 15-12-2011
DOI: 10.1242/JEB.057349
Abstract: Viviparous reptiles have been used as model species for many studies that seek to explain the evolution of viviparity. The vast majority of such studies have focused on the advantage viviparity provides with regards to maternal control of embryonic developmental temperature. However, viviparity may also allow increased control of nutrient transfer, such that mothers adaptively manipulate offspring phenotype through varying maternal nutritional support. Because maternal nutritional transfer is temperature dependent, maternal nutritional strategies may vary between climatically distinct populations. In this study we used an orthogonal experimental design in which mothers and offspring from climatically distinct populations of a viviparous skink (Niveoscincus ocellatus) were allocated randomly to either a protein-rich or a protein-poor diet. Our results suggest that N. ocellatus mothers are able to compensate for sub-optimal nutritional conditions and can adaptively manipulate offspring phenotype to best fit the postnatal nutritional environment. Furthermore, maternal nutritional strategies appear to vary between climatically distinct populations. These results suggest that in viviparous reptiles, matrotrophy provides a means of producing an adaptive offspring phenotype, in addition to maternal control of developmental temperature.
Giving offspring a head start in life: field and experimental evidence for selection on maternal basking behaviour in lizards
Publisher: Wiley
Date: 25-01-2010
DOI: 10.1111/J.1420-9101.2009.01924.X
Abstract: The timing of birth is often correlated with offspring fitness in animals, but experimental studies that disentangle direct effects of parturition date and indirect effects mediated via variation in female traits are rare. In viviparous ectotherms, parturition date is largely driven by female thermal conditions, particularly maternal basking strategies. Our field and laboratory studies of a viviparous lizard (Niveoscincus ocellatus) show that earlier-born offspring are more likely to survive through their first winter and are larger following that winter, than are later-born conspecifics. Thus, the association between parturition date and offspring fitness is causal, rather than reflecting an underlying correlation between parturition date and maternal attributes. Survival selection on offspring confers a significant advantage for increased maternal basking in this species, mediated through fitness advantages of earlier parturition. We discuss the roles of environmentally imposed constraints and parent-offspring conflict in the evolution of maternal effects on parturition date.
Development of 13 microsatellite loci in the spotted snow skink Niveoscincus ocellatus (Squamata: Scincidae)
Publisher: Springer Science and Business Media LLC
Date: 11-11-2010
Are there physiological constraints on maternal ability to adjust sex ratios in mammals?
Publisher: Wiley
Date: 03-2016
DOI: 10.1111/JZO.12327
Do Gravid Females Become Selfish? Female Allocation of Energy during Gestation
Publisher: University of Chicago Press
Date: 05-2012
DOI: 10.1086/665567
Abstract: Net energy availability depends on plasma corticosterone concentrations, food availability, and their interaction. Limited net energy availability requires energy trade-offs between self-maintenance and reproduction. This is important in matrotrophic viviparous animals because they provide large amounts of energy for embryos, as well as self-maintenance, for the extended period of time during gestation. In addition, gravid females may transmit environmental information to the embryos in order to adjust offspring phenotype. We investigated effects of variation in maternal plasma corticosterone concentration and maternal food availability (2 × 2 factorial design) during gestation on offspring phenotype in a matrotrophic viviparous lizard (Pseudemoia entrecasteauxii). Subsequently, we tested preadaptation of offspring phenotype to their postnatal environment by measuring risk-averse behavior and growth rate using reciprocal transplant experiments. We found that maternal net energy availability affected postpartum maternal body condition, offspring snout-vent length, offspring mass, offspring performance ability, and offspring fat reserves. Females treated with corticosterone allocated large amounts of energy to their own body condition, and their embryos allocated more energy to energy reserves than somatic growth. Further, offspring from females in high plasma corticosterone concentration showed compensatory growth. These findings suggest that while females may be selfish when gestation conditions are stressful, the embryos may adjust their phenotype to cope with the postnatal environment.
Sexual dimorphism in lizard body shape: The role of sexual selection and fecundity selection
Publisher: Wiley
Date: 07-2002
DOI: 10.1111/J.0014-3820.2002.TB01464.X
Abstract: Sexual dimorphism is widespread in lizards, with the most consistently dimorphic traits being head size (males have larger heads) and trunk length (the distance between the front and hind legs is greater in females). These dimorphisms have generally been interpreted as follows: (1) large heads in males evolve through male-male rivalry (sexual selection) and (2) larger interlimb lengths in females provide space for more eggs (fecundity selection). In an Australian lizard (the snow skink, Niveoscincus microlepidotus), we found no evidence for ongoing selection on head size. Trunk length, however, was under positive fecundity selection in females and under negative sexual selection in males. Thus, fecundity selection and sexual selection work in concert to drive the evolution of sexual dimorphism in trunk length in snow skinks.
Developmental Biology: Embryonic Movement Influences Sex Determination in a Turtle
Publisher: Elsevier BV
Date: 09-2019
DOI: 10.1016/J.CUB.2019.07.080
Abstract: Many ectotherms behaviourally thermoregulate to maintain their body temperatures within an optimal range. A new study suggests that turtle embryos developing inside eggs also have this capacity, and that this can have significant implications for sex determination.
Degrees of change: between and within population variation in thermal reaction norms of phenology in a viviparous lizard
Publisher: Wiley
Date: 19-08-2020
DOI: 10.1002/ECY.3136
Haldane rules: costs of outbreeding at production of daughters in sand lizards
Publisher: Wiley
Date: 26-08-2004
Plastic rates of development and the effect of thermal extremes on offspring fitness in a cold‐climate viviparous lizard
Publisher: Wiley
Date: 04-2018
DOI: 10.1002/JEZ.2167
Abstract: Populations at the climatic margins of a species' distribution can be exposed to conditions that cause developmental stress, resulting in developmental abnormalities. Even within the thermal range of normal development, phenotypes often vary with developmental temperature (i.e., thermal phenotypic plasticity). These effects can have significant consequences for organismal fitness and, thus, population persistence. Reptiles, as ectotherms, are particularly vulnerable to thermal effects on development and are, therefore, considered to be at comparatively high risk from changing climates. Understanding the extent and direction of thermal effects on phenotypes and their fitness consequences is crucial if we are to make meaningful predictions of how populations and species will respond as climates warm. Here, we experimentally manipulated the thermal conditions experienced by females from a high-altitude, cold-adapted population of the viviparous skink, Niveoscincus ocellatus, to examine the consequences of thermal conditions at the margins of this population's normal temperature range. We found strong effects of thermal conditions on the development of key phenotypic traits that have implications for fitness. Specifically, we found that offspring born earlier as a result of high temperatures during gestation had increased growth over the first winter of life, but there was no effect on offspring survival, nor was there an effect of developmental temperature on the incidence of developmental abnormalities. Combined, our results suggest that advancing birth dates that result from warming climates may have positive effects in this population via increased growth.
Differential sex allocation in sand lizards: bright males induce daughter production in a species with heteromorphic sex chromosomes
Publisher: The Royal Society
Date: 28-06-2005
Abstract: In sand lizards ( Lacerta agilis ), males with more and brighter nuptial coloration also have more DNA fragments visualized in restriction fragment length polymorphism analysis of their major histocompatibility complex class I loci (and, hence, are probably more heterozygous at these loci). Such males produce more viable offspring, with a particularly strong viability effect on daughters. This suggests that females should adjust both their reproductive investment and offspring sex ratio in relation to male coloration (i.e. differential allocation). Our results show that experimental manipulation of partner coloration in the wild results in significantly higher maternal effort and a 10% higher proportion of daughters than sons. This supports the hypothesis that females increase their maternal energetic expenditure and adjust their offspring sex ratio in response to high-quality partners. However, it also suggests that this has probably evolved through natural selection for increased offspring viability (primarily through production of daughters), rather than through increased mate attraction (e.g. sexy sons).
Potential for thermal tolerance to mediate climate change effects on three members of a cool temperate lizard genus, Niveoscincus
Publisher: Elsevier BV
Date: 08-2015
DOI: 10.1016/J.JTHERBIO.2015.05.002
Abstract: Climatic changes are predicted to be greater in higher latitude and mountainous regions but species specific impacts are difficult to predict. This is partly due to inter-specific variance in the physiological traits which mediate environmental temperature effects at the organismal level. We examined variation in the critical thermal minimum (CTmin), critical thermal maximum (CTmax) and evaporative water loss rates (EWL) of a widespread lowland (Niveoscincus ocellatus) and two range restricted highland (N. microlepidotus and N. greeni) members of a cool temperate Tasmanian lizard genus. The widespread lowland species had significantly higher CTmin and CTmax and significantly lower EWL than both highland species. Implications of inter-specific variation in thermal tolerance for activity were examined under contemporary and future climate change scenarios. Instances of air temperatures below CTmin were predicted to decline in frequency for the widespread lowland and both highland species. Air temperatures of high altitude sites were not predicted to exceed the CTmax of either highland species throughout the 21st century. In contrast, the widespread lowland species is predicted to experience air temperatures in excess of CTmax on 1 or 2 days by three of six global circulation models from 2068-2096. To estimate climate change effects on activity we reran the thermal tolerance models using minimum and maximum temperatures selected for activity. A net gain in available activity time was predicted under climate change for all three species while air temperatures were predicted to exceed maximum temperatures selected for activity with increasing frequency, the change was not as great as the predicted decline in air temperatures below minimum temperatures selected for activity. We hypothesise that the major effect of rising air temperatures under climate change is an increase in available activity period for both the widespread lowland and highland species. The consequences of a greater available activity period will depend on the extent to which changes in climate alters other related factors, such as the nature and level of competition between the respective species.
Geographical differences in maternal basking behaviour and offspring growth rate in a climatically widespread viviparous reptile
Publisher: The Company of Biologists
Date: 2013
DOI: 10.1242/JEB.089953
Abstract: In reptiles, the thermal environment during embryonic development affects offspring phenotypic traits and potentially offspring fitness. In viviparous species, mothers can potentially manipulate the embryonic thermal environment through their basking behaviour and, thus, may be able to manipulate offspring phenotype and increase offspring fitness. One way mothers can increase offspring fitness is by fine-tuning their basking behaviour to the environment in order to buffer the embryo from deleterious developmental temperatures. In widespread species, it is unclear whether populations that have evolved under different climatic conditions will exhibit different maternal behaviours and/or thermal effects on offspring fitness. To test this, we provided extended or reduced basking opportunity to gravid spotted skinks (Niveoscincus ocellatus) and their offspring from two populations at the climatic extremes of the species distribution. Gravid females fine-tuned their basking behaviour to the basking opportunity, which allowed them to buffer their embryos from potentially negative thermal effects. This fine-tuning of female basking behaviour appears to have led to the expression of geographical differences in basking behaviour with females from the cold alpine regions being more opportunistic in their basking behaviour than females from the warmer regions. However, those differences in maternal behaviour did not preclude the evolution of geographic differences in thermal effects: offspring growth varied between populations potentially suggesting local adaptation to basking conditions. Our results demonstrate that maternal effects and phenotypic plasticity can play a significant role in allowing species to cope in changing environmental conditions, which is particularly relevant in the context of climate change.
Biodiversity redistribution under climate change: Impacts on ecosystems and human well-being.
Publisher: American Association for the Advancement of Science (AAAS)
Date: 31-03-2017
Abstract: Distributions of Earth's species are changing at accelerating rates, increasingly driven by human-mediated climate change. Such changes are already altering the composition of ecological communities, but beyond conservation of natural systems, how and why does this matter? We review evidence that climate-driven species redistribution at regional to global scales affects ecosystem functioning, human well-being, and the dynamics of climate change itself. Production of natural resources required for food security, patterns of disease transmission, and processes of carbon sequestration are all altered by changes in species distribution. Consideration of these effects of bio ersity redistribution is critical yet lacking in most mitigation and adaptation strategies, including the United Nation's Sustainable Development Goals.
The role of body size in competition and mate choice in an agamid with female-biased size dimorphism
Publisher: Brill
Date: 2007
Female aggression predicts mode of paternity acquisition in a social lizard
Publisher: The Royal Society
Date: 04-03-2009
Abstract: In idual differences in behaviour are ubiquitous in nature. Despite the likely role of selection in maintaining these differences, there are few demonstrations of their fitness consequences in wild populations and, consequently, the mechanisms that link behavioural variation to variation in fitness are poorly understood. Specifically, the consequences of consistent in idual differences in behaviour for the evolution of social and mating strategies have rarely been considered. We examined the functional links between variation in female aggression and her social and mating strategies in a wild population of the social lizard Egernia whitii . We show that female Egernia exhibit temporally consistent aggressive phenotypes, which are unrelated to body size, territory size or social density. A female's aggressive phenotype, however, has strong links to her mode of paternity acquisition (within- versus extra-pair paternity), with more aggressive females having more offspring sired by extra-pair males than less aggressive females. We discuss the potential mechanisms by which female aggression could underpin mating strategies, such as the pursuit/acceptance of extra-pair copulations. We propose that a deeper understanding of the evolution and maintenance of social and mating systems may result from an explicit focus on in idual-level female behavioural phenotypes and their relationship with key reproductive strategies.
Integrating the Development of Professional Skills Throughout an ICT Curriculum Improves a Graduate’s Competency
Publisher: Springer International Publishing
Date: 2021
Geographic and annual variation in reproductive cycles in the Tasmanian spotted snow skink, Niveoscincus ocellatus (Squamata : Scincidae)
Publisher: CSIRO Publishing
Date: 1999
DOI: 10.1071/ZO99038
Abstract: We studied the reproductive cycle of two populations of the spotted snow skink, Niveoscincus ocellatus, over a three-year period. This species is widespread in Tasmania and its distribution overlaps those of other species in the genus that show two distinct reproductive strategies: annual reproduction that is completed within one season, and biennial reproduction in which females carry advanced embryos throughout winter hibernation. We chose populations representative of the climatic extremes of the species’ distribution, within these areas of overlap. Niveoscincus ocellatus maintains the same basic reproductive strategy in both populations: summer gestation, primary autumn mating with obligate sperm storage by females, secondary mating in spring, and predominantly spring vitellogenesis and ovulation. In both populations all females reproduce annually, suggesting that reproductive frequency is not constrained by availability of energy. However, we found distinct differences in the timing of ovulation and parturition. Females from our subalpine site ovulated approximately one month later than those from our warmer, lowland site parturition was delayed by the same period so gestation length was unchanged. The delay in ovulation results in gestation proceeding over the warmest months at the cold site. The annual reproductive cycle of this species appears to constrain its distribution to the lower altitudinal/climatic range of alpine Niveoscincus species. There were minor annual differences in the timing of reproductive events at each site, which we attribute to variation in thermal conditions and the amount of precipitation.
Differences in homomorphic sex chromosomes are associated with population divergence in sex determination in Carinascincus ocellatus (Scincidae: Lygosominae)
Publisher: MDPI AG
Date: 02-2021
Abstract: Sex determination directs development as male or female in sexually reproducing organisms. Evolutionary transitions in sex determination have occurred frequently, suggesting simple mechanisms behind the transitions, yet their detail remains elusive. Here we explore the links between mechanisms of transitions in sex determination and sex chromosome evolution at both recent and deeper temporal scales ( Myr ~79 Myr). We studied a rare ex le of a species with intraspecific variation in sex determination, Carinascincus ocellatus, and a relative, Liopholis whitii, using c-banding and mapping of repeat motifs and a custom Y chromosome probe set to identify the sex chromosomes. We identified both unique and conserved regions of the Y chromosome among C. ocellatus populations differing in sex determination. There was no evidence for homology of sex chromosomes between C. ocellatus and L. whitii, suggesting independent evolutionary origins. We discuss sex chromosome homology between members of the subfamily Lygosominae and propose links between sex chromosome evolution, sex determination transitions, and karyotype evolution.
Empirical Analysis of Strategies Employed Within an ICT Curriculum to Increase the Quantity of Graduates
Publisher: Springer International Publishing
Date: 2021
Sex Allocation and Sex Determination in Squamate Reptiles
Publisher: S. Karger AG
Date: 29-12-2009
DOI: 10.1159/000272459
Abstract: Reptiles possess a wide variety of sex determining mechanisms, more so than any other vertebrate group. They offer outstanding opportunities to understand the evolutionary transitions between modes of sex determination. In this review, we argue that sex allocation theory is fundamental for understanding the selective causes of such shifts. Whether selection for biased sex allocation actually results in evolutionary shifts in sex determination depends on the overall strength, direction and consistency of selection and to what extent existing reproductive systems can establish novel links between factors causing sex-specific fitness and mechanisms of sex determination. Perhaps one of the most exciting advances in recent years has been the phylogenetically erse range in reptile taxa that form the basis of research on the evolution of sex determination. The traditional use of long-lived oviparous species (especially turtles and crocodiles) is now expanded to include a range of short-lived taxa that exhibit both genetic sex determination and environment-/temperature-dependent sex determination (particularly agamid lizards), as well as a greater emphasis on viviparous species. If selection on differential sex allocation is a key selective pressure for the evolution of sex-determining mechanisms, these taxa will provide considerable insights into the integrated fields of sex allocation biology and sex determination.
Offspring‐driven local dispersal in female sand lizards (Lacerta agilis)
Publisher: Wiley
Date: 30-09-2004
DOI: 10.1111/J.1420-9101.2004.00798.X
Abstract: We report on a field study in which determinants of female breeding dispersal (i.e. the shift in the mean home range coordinates between successive breeding events) was investigated. Offspring were released in full sib groups (or half sib ones if there was within-clutch multiple paternity) at a separation distance from the females that varied between 'families'. This allowed for analysis of 'offspring nearness' effects on maternal dispersal. When a female's offspring were released more closely to her, she responded with greater dispersal. Furthermore, when the data set was truncated at 100 m maternal-offspring separation distance at offspring release (because perception at longer distances is likely to be unrealistic), maternal dispersal resulted in greater separation distance between female and offspring in the following year. A corresponding analysis for juveniles revealed no effect of maternal nearness on offspring dispersal but identified a significant effect of clutch size, to our surprise with dispersal declining with increasing clutch size. We discuss this result in a context of the 'public information hypothesis' (reinterpreted for juveniles in a nonsocial foraging species), suggesting that conspecific abundance perhaps acts as an indicator of local habitat quality. Thus, our analysis suggests a microgeographic structuring of the adult female population driven by genetic factors, either through inbreeding avoidance, or from simply avoiding in iduals with a similar genotype regardless of their pedigree relatedness, while a nongenetic factor seems more important in their offspring.
Repeatable intra-individual variation in plasma testosterone concentration and its sex-specific link to aggression in a social lizard
Publisher: Elsevier BV
Date: 07-2010
DOI: 10.1016/J.YHBEH.2010.03.016
Abstract: In idual hormone profiles can be important generators of phenotypic variation. Despite this, work on the consequences of hormone profiles has traditionally ignored the large inter-in idual variation within natural populations. However, recent research has advocated the need to explicitly consider this variation and address its consequences for selection. One of the key steps in this process is examining repeatability in hormone profiles and their links to behavioral traits under selection. In this study we show that in iduals within a free-ranging population of the Australian lizard Egernia whitii exhibit temporal repeatability in their circulating baseline testosterone concentrations as well as their aggressive response towards conspecific intruders. Furthermore, we show significant, sex-specific links between testosterone and aggression. Specifically, testosterone and aggression is negatively linked in males, while there is no relationship in females. As conspecific aggression has significant consequences for fitness-related traits (parental care, mating strategies) in this species, inter-in idual variation in testosterone concentrations, through their effects on aggression, could have important implications for in idual fitness. We discuss the potential causes and consequences of hormonal repeatability as well as provide explanations for its sex-specific links with aggression. Specifically, we suggest that these patterns are the result of alternative hormonal pathways governing aggression within Egernia and may indicate a decoupling of aggression and testosterone across the sexes.
Context-dependent thermolability of sex determination in a lacertid lizard with heteromorphic sex chromosomes
Publisher: The Company of Biologists
Date: 15-05-2023
DOI: 10.1242/BIO.059967
Abstract: Developmental conditions can profoundly impact key life history traits of the in idual. In cases where offspring sex is driven by developmental reaction norms, permanent changes to the phenotype can fundamentally alter life history trajectories. Sex determination mechanisms in reptiles are remarkably erse, including well-characterised genetic and temperature-dependent sex determination. In rarer, but increasingly more commonly documented cases, sex can also be determined by a combination of the two, with temperature overriding the genetically determined sex. Thus, sex-by-temperature interactions is a mechanism that can be contextually labile, where reaction norms of sex against developmental environment might only be observable under certain conditions. We examine the effects of incubation temperature on hatchling sex in an oviparous lizard with clearly defined heteromorphic sex chromosomes presumed to determine sex solely on a genetic basis. We also test the repeatability of our results by replicating incubation experiments across 3 years. We show that warmer temperatures may override chromosomal sex and cause an overproduction of daughters. However, this effect was inconsistent among years, with high temperature only resulting in a daughter-significant bias in one year. Warm-incubated daughters were more efficient at converting yolk into tissue, which would allow for greater resource allocation to other fitness-related processes, such as growth. This suggests that thermolabile sex determination could be a trait under selection. More energy-efficient embryos also produced faster-growing offspring, suggesting that energy utilization patterns of the embryo were maintained into the juvenile stage, which could have important implications for the ontogenetic development and evolution of life histories.
Effect of MHC and inbreeding on disassortative reproduction: A data revisit, extension and inclusion of fertilization in sand lizards
Publisher: Wiley
Date: 03-2023
DOI: 10.1002/ECE3.9934
Abstract: The harmful effects of close inbreeding have been recognized for centuries and, with the rise of Mendelian genetics, was realized to be an effect of homozygosis. This historical background led to great interest in ways to quantify inbreeding, its depression effects on the phenotype and flow‐on effects on mate choice and other aspects of behavioral ecology. The mechanisms and cues used to avoid inbreeding are varied and include major histocompatibility complex (MHC) molecules and the peptides they transport as predictors of the degree of genetic relatedness. Here, we revisit and complement data from a Swedish population of sand lizards ( Lacerta agilis ) showing signs of inbreeding depression to assess the effects of genetic relatedness on pair formation in the wild. Parental pairs were less similar at the MHC than expected under random mating but mated at random with respect to microsatellite relatedness. MHC clustered in groups of RFLP bands but no partner preference was observed with respect to partner MHC cluster genotype. Male MHC band patterns were unrelated to their fertilization success in clutches selected for analysis on the basis of showing mixed paternity. Thus, our data suggest that MHC plays a role in pre‐copulatory, but not post‐copulatory partner association, suggesting that MHC is not the driver of fertilization bias and gamete recognition in sand lizards.
Energy expenditure of the spotted snow skink, Niveoscincus ocellatus, at two climatic extremes of its distribution range
Publisher: Elsevier BV
Date: 08-2015
DOI: 10.1016/J.JTHERBIO.2015.07.003
Abstract: The study of energy expenditure between populations of a wide ranging ectothermic species may provide an insight into how organisms respond to variation in environmental conditions. In this study, the energy expenditure of male spotted snow skinks, Niveoscincus ocellatus, living at the two extremes of the species' distribution range (warm lowland versus cold alpine site) was measured using the doubly labelled water method. Males at the cold alpine site expended more energy per gram per hour compared to their counterparts living at the warm lowland site. Lizards living at high altitude were active at lower temperatures compared with those at the low altitude site, which resulted in a longer activity time for the highland population. However, the differences in energy expenditure cannot be explained only by these differences in activity time. We further suggest that at the cold alpine site, lizards compensated for the low temperatures by elevating their metabolism which subsequently increased their energy expenditure. An elevated metabolic rate combined with modified thermoregulatory behaviour is likely an important mechanism allowing N. ocellatus to cope with the cold environments at high altitude sites.
Effects of male telomeres on probability of paternity in sand lizards
Publisher: The Royal Society
Date: 08-2018
Abstract: Standardized swim-up trials are used in in vitro fertilization clinics to select particularly motile spermatozoa in order to increase the probability of a successful fertilization. Such trials demonstrate that sperm with longer telomeres have higher motility and lower levels of DNA damage. Regardless of whether sperm motility, and successful swim-up to fertilization sites, is a direct or correlational effect of telomere length or DNA damage, covariation between telomere length and sperm performance predicts a relationship between telomere length and probability of paternity in sperm competition, a prediction that for ethical reasons cannot be tested on humans. Here, we test this prediction in sand lizards ( Lacerta agilis ) using experimental data from twice-mated females in a laboratory population, and telomere length in blood from the participating lizards. Female identity influenced paternity (while the mechanism was not identified), while relatively longer male telomeres predicted higher probability of paternity. We discuss potential mechanisms underpinning this result.
Within-population variation in ejaculate characteristics in a prolonged breeder, Peron's tree frog, Litoria peronii
Publisher: Springer Science and Business Media LLC
Date: 11-07-2008
DOI: 10.1007/S00114-008-0423-7
Abstract: Sperm number is often a good predictor of success in sperm competition however, it has become increasingly clear that, for some species, variation in probability of paternity cannot be explained by sperm number alone. Intraspecific variation in ejaculate characteristics, such as the number of viable sperm and sperm longevity, may play an equally important role in determining fertilization success. Here, we assess variation among ejaculates in three factors that may contribute to fertilization success (number of sperm per ejaculate, viability, and longevity), in a population of Peron's tree frog (Litoria peronii). We detected large variation among males in the number of sperm per ejaculate and the proportion of viable sperm within ejaculates, which could not be explained by variation in either male size or body condition. However, the proportion of viable sperm released by males increased over the season. Finally, we assessed sperm longevity (proportion viable sperm determined using a dual-fluorochrome vital dye) at two different temperatures. At 23 degrees C, on average, 75% of sperm remained viable after 2 h, but there were significant differences amongst males with the percentage of viable sperm ranging from 43% to 95%. For sperm incubated at 4 degrees C, ejaculates varied fivefold in sperm longevity with some males having 50% viable sperm after 5 days. Our data suggest that ejaculate characteristics (sperm number, viability, and longevity) vary widely in Peron's tree frog and may therefore play an important role in determining siring success both in the presence and absence of sperm competition. We discuss the results in relation to selection on ejaculate traits via natural and sexual selection in this and other hibians.
Extreme plasticity in reproductive biology of an oviparous lizard
Publisher: Wiley
Date: 11-06-2018
DOI: 10.1002/ECE3.4247
A comparative study of cell growth on a cold sprayed Ti–Ta composite
Publisher: Elsevier BV
Date: 06-2020
Costly parasite resistance: a genotype-dependent handicap in sand lizards?
Publisher: The Royal Society
Date: 11-07-2005
Abstract: Male sand lizards ( Lacerta agilis ) with a specific restriction fragment length polymorphism fragment in their major histocompatibility complex (MHC) genotype (‘O-males’) are more resistant to ectoparasites (a tick, Ixodes ricinus ) than are males that lack this fragment (‘NO-males’). However, emerging evidence suggests that such adaptive immune responses are costly, here manifested by reduced body condition and a compromised defence against secondary infections by haemoprotid parasites that use the ticks as vectors. Subsequent to tick encounter, O-males suffer from a higher leucocyte–erythrocyte ratio, and higher haemoprotid parasitaemia, in particular in relation to vector encounter rate. Furthermore, O-males (i.e. successful tick defenders) with more haemoprotid parasites remaining in their blood stream were in better body condition, whereas this did not apply in NO-males, demonstrating that the adaptive immunoreaction can—in the short term—be energetically even more costly than being moderately parasitized. In agreement with Zahavian handicap theory, O-males had a (marginally) higher reproductive success than males that lacked this fragment.
Disentangling sex allocation in a viviparous reptile with temperature‐dependent sex determination: a multifactorial approach
Publisher: Wiley
Date: 16-12-2017
DOI: 10.1111/JEB.13219
Abstract: Females are predicted to alter sex allocation when ecological, physiological and behavioural variables have different consequences on the fitness of male and female offspring. Traditionally, tests of sex allocation have examined single causative factors, often ignoring possible interactions between multiple factors. Here, we used a multifactorial approach to examine sex allocation in the viviparous skink, Niveoscincus ocellatus. We integrated a 16-year observational field study with a manipulative laboratory experiment to explore whether the effects of the maternal thermal environment interact with the resources available to females for reproduction to affect sex allocation decisions. We found strong effects of temperature on sex allocation in the field, with females born in warm conditions and males in cold conditions however, this was not replicated in the laboratory. In contrast, we found no effect of female resource availability on sex allocation, either independently, or in interaction with temperature. These results corresponded with an overall lack of an effect of resource availability on any of the life history traits that we predicted would mediate the benefits of differential sex allocation in this system, suggesting that selection for sex allocation in response to resource availability may be relatively weak. Combined, these results suggest that temperature may be the predominant factor driving sex allocation in this system.
The Evolution of Polyandry and Patterns of Multiple Paternity in Lizards
Publisher: CRC Press
Date: 19-12-2014
DOI: 10.1201/B17961-17
Aggression, but not testosterone, is associated to oxidative status in a free-living vertebrate
Publisher: Brill
Date: 2011
Sexual differences in telomere selection in the wild
Publisher: Wiley
Date: 12-04-2011
Conservation of sex-linked markers among conspecific populations of a viviparous skink, Niveoscincus occllatus, exhibiting genetic and temperature-dependent sex determination
Publisher: Oxford University Press (OUP)
Date: 05-03-2018
DOI: 10.1093/GBE/EVY042
Variation in social organization influences the opportunity for sexual selection in a social lizard
Publisher: Wiley
Date: 28-12-2010
A Novel Pattern of Placental Leucine Transfer During Mid to Late Gestation in a Highly Placentotrophic Viviparous Lizard
Publisher: Wiley
Date: 06-2012
DOI: 10.1002/JEZ.B.22446
Abstract: Placentotrophy is the nourishment of embryos by resources provided via the placenta during gestation. The magnitude and timing of placental nutrient support during pregnancy are important for embryonic growth, especially in highly placentotrophic animals such as mammals. However, no study has yet investigated how placental organic nutrient support may change during pregnancy in highly placentotrophic viviparous reptiles. Amino acids are essential nutrients for embryonic growth and leucine is a common amino acid. The magnitude and timing of placental leucine transfer may affect embryonic growth and mass and, therefore, offspring phenotype. In this study, female Pseudemoia entrecasteauxii, a highly placentotrophic viviparous skink, were collected throughout gestation. We injected (3)H-leucine into these gravid females and assessed the transfer of (3)H-leucine into maternal compartments (i.e., the blood and the liver), and into embryonic compartments (i.e., the embryo, the yolk, and the amniotic fluid). At either 60 or 120 min post-injection, the radioactivity in each s le was extracted and then counted, and the transfer ratio was calculated. Our results provide direct evidence that circulating maternal leucine passes through the placenta into the embryos in this species. The relative rate of placental leucine transfer did not alter during mid to late gestation. This suggests the steady somatic growth of the embryos during mid-late pregnancy is dependent upon the placental transfer of nutrients rather than yolk stores. This pattern of placental nutrient support may determine offspring body size at birth and, therefore, offspring fitness in P. entrecasteauxii.
Testosterone, ticks and travels: a test of the immunocompetence-handicap hypothesis in free-ranging male sand lizards
Publisher: The Royal Society
Date: 22-11-2000
Fecundity and MHC affects ejaculation tactics and paternity bias in sand lizards
Publisher: Wiley
Date: 04-2004
DOI: 10.1111/J.0014-3820.2004.TB00423.X
Abstract: We demonstrate that extending copulation enhances probability of paternity in sand lizards and that determinants of copulation duration depend on a males' mating order (first or second). First males, with no information on presence of rivals, extend copulation when mating with a more fecund female. Second males, however, adjust copula duration in relation to a first male's relatedness with his female, which there is reason to believe can be deduced from the MHC-related odor of the copulatory plug. Male-female relatedness negatively influences a male's probability of paternity, and when second males are in a favored role (i.e., the first male is the one more closely related to the female), second males transfer larger ejaculates, resulting in higher probability of paternity. This result corroborates predictions from recent theoretical models on sperm expenditure theory incorporating cryptic female choice and sexual conflict. More specifically, the results conform to a "random roles" model, which depicts males as being favored by some females and disfavored by others, but not to a "constant-type" model, in which a male is either favored or disfavored uniformly by all females in a population.
Australian lizards are outstanding models for reproductive biology research
Publisher: CSIRO Publishing
Date: 28-09-2020
DOI: 10.1071/ZO21017
Abstract: Australian lizards are a erse group distributed across the continent and inhabiting a wide range of environments. Together, they exhibit a remarkable ersity of reproductive morphologies, physiologies, and behaviours that is broadly representative of vertebrates in general. Many reproductive traits exhibited by Australian lizards have evolved independently in multiple lizard lineages, including sociality, complex signalling and mating systems, viviparity, and temperature-dependent sex determination. Australian lizards are thus outstanding model organisms for testing hypotheses about how reproductive traits function and evolve, and they provide an important basis of comparison with other animals that exhibit similar traits. We review how research on Australian lizard reproduction has contributed to answering broader evolutionary and ecological questions that apply to animals in general. We focus on reproductive traits, processes, and strategies that are important areas of current research, including behaviours and signalling involved in courtship mechanisms involved in mating, egg production, and sperm competition nesting and gestation sex determination and finally, birth in viviparous species. We use our review to identify important questions that emerge from an understanding of this body of research when considered holistically. Finally, we identify additional research questions within each topic that Australian lizards are well suited for reproductive biologists to address.
Ectothermic telomeres: It’s time they came in from the cold
Publisher: The Royal Society
Date: 15-01-2018
Abstract: We review the evolutionary ecology and genetics of telomeres in taxa that cannot elevate their body temperature to a preferred level through metabolism but do so by basking or seeking out a warm environment. This group of organisms contains all living things on earth, apart from birds and mammals. One reason for our interest in this synthetic group is the argument that high, stable body temperature increases the risk of malignant tumours if long, telomerase-restored telomeres make cells ‘live forever’. If this holds true, ectotherms should have significantly lower cancer frequencies. We discuss to what degree there is support for this ‘anti-cancer’ hypothesis in the current literature. Importantly, we suggest that ectothermic taxa, with variation in somatic telomerase expression across tissue and taxa, may hold the key to understanding ongoing selection and evolution of telomerase dynamics in the wild. We further review endotherm-specific effects of growth on telomeres, effects of autotomy (‘tail dropping’) on telomere attrition, and costs of maintaining sexual displays measured in telomere attrition. Finally, we cover plant ectotherm telomeres and life histories in a separate ‘mini review’. This article is part of the theme issue ‘Understanding ersity in telomere dynamics'.
Yolk contributes steroid to the multidimensional endocrine environment of embryos of Niveoscincus metallicus, a viviparous skink with a moderately complex placenta
Publisher: Elsevier BV
Date: 05-2014
DOI: 10.1016/J.CBPA.2014.02.013
Abstract: Maternally-derived testosterone (T) and 17-β-oestradiol (E2) provide epigenetic mechanisms by which mothers can actively influence offspring phenotype. In amniotes, maternal steroids may be derived from yolk or transferred across the placenta according to parity mode. Viviparous reptiles utilise both a yolk and a placenta to support their developing embryos, but it has not yet been confirmed whether yolk is a source of maternal T and E2 in such species. We investigated this question using the viviparous lizard Niveoscincus metallicus as our model species. We measured T and E2 in the yolks during vitellogenesis, immediately post-ovulation and at progressive stages of gestation. Our results confirm that yolk is a substantial source of T and E2 in N. metallicus. Contrary to the pattern seen in many oviparous species, we did not observe a marked decline in yolk concentrations of either T or E2 after the initiation of sexual differentiation in the embryos. Rather, we found no statistically significant decline in yolk concentrations of both T and E2 post-ovulation. In viviparous reptiles that utilise both yolk and placenta to nourish their embryos, yolk likely plays an important role in these dynamics but that role is not yet clear. Further research is warranted to understand the importance of yolk steroids in the endocrine environment of the developing viviparous reptile.
Offspring size-number strategies: Experimental manipulation of offspring size in a viviparous lizard (Lacerta vivipara)
Publisher: Wiley
Date: 02-2002
Can teacher collaboration overcome barriers to interdisciplinary learning in a disciplinary university? A case study using climate change
Publisher: Informa UK Limited
Date: 10-2012
Inbreeding effects on telomeres in hatchling sand lizards (Lacerta agilis): An optimal family affair?
Publisher: Wiley
Date: 19-10-2022
DOI: 10.1111/MEC.16723
Abstract: Telomeres are nucleotide‐protein caps, predominantly at the ends of Metazoan linear chromosomes, showing complex dynamics with regard to their lengthening and shortening through life. Their complexity has entertained the idea that net telomere length and attrition could be valuable biomarkers of phenotypic and genetic quality of their bearer. Intuitively, those in iduals could be more heterozygous and, hence, less inbred. However, some inbred taxa have longer, not shorter, telomeres. To understand the role of inbreeding in this complex scenario we need large s les across a range of genotypes with known maternity and paternity in telomere‐screened organisms under natural conditions. We assessed the effects of parental and hatchling inbreeding on telomere length in offspring from sires and dams in a population of sand lizards ( Lacerta agilis ). Maternal and paternal ID and their interactions predict hatchling telomere length at substantial effect sizes ( R 2 .50). Deviation from mean maternal heterozygosity statistically predicts shorter offspring telomeres but this only when sibship is controlled for by paternal ID, and then is still limited ( R 2 = .06). Raw maternal heterozygosity scores, ignoring absolute deviation from the mean, explained 0.07% of the variance in hatchling telomere length. In conclusion, inbreeding is not a driver of telomere dynamics in the sand lizard ( Lacerta agilis ) study system.
Complex selection associated with Hox genes in a natural population of lizards
Publisher: Wiley
Date: 23-08-2011
DOI: 10.1111/J.1420-9101.2011.02368.X
Abstract: Hox genes are recognized for their explanatory power of bilateral development. However, relatively little is known about natural variation in, and the evolutionary dynamics of, Hox genes within wild populations. Utilizing a natural population of sand lizards (Lacerta agilis), we screened HoxA13 for genetic variation and an association with incidence of offspring malformations. We found significant effects of parental genetic similarity and offspring sex, and their interaction, on risk of hatching malformed as an offspring. We also found within population genetic variation in HoxA13, and identified a significant effect of a three-way interaction among Hox genotype, parental genetic similarity, and offspring sex on the risk of hatching malformation. Since malformed offspring in this population do not survive to maturity, this study reveals complex and ongoing selection associated with Hox genes in a wild reptile population. Importantly, this demonstrates the utility of natural populations in unveiling microevolutionary processes shaping variation in highly conserved genes.
Long term effects of outbreeding: experimental founding of island population eliminates malformations and improves hatching success in sand lizards
Publisher: Elsevier BV
Date: 09-2020
Are there benefits to being born asynchronously: an experimental test in a social lizard
Publisher: Oxford University Press (OUP)
Date: 21-11-2007
Size dimorphism in Rankinia [Tympanocryptis] diemensis (Family Agamidae): sex-specific patterns and geographic variation
Publisher: Oxford University Press (OUP)
Date: 25-07-2008
Feeding Ecology of the Tasmanian Spotted Skink, Niveoscincus Ocellatus (Squamata: Scincidae)
Publisher: CSIRO Publishing
Date: 1996
DOI: 10.1071/ZO9960205
Abstract: The feeding ecology of the spotted skink, Niveoscincus ocellatus, was examined over a 6-month period, from October to March, with additional data from one s le in midwinter. The investigation considered feeding activity, dietary composition and foraging strategy. Feeding activity,measured by stomach fullness, was unrelated to age, sex or reproductive status and showed little variation during the warmer months in winter feeding was greatly reduced. N. ocellatus exhibits flexible foraging behaviour a wide variety of terrestrial arthropods is taken opportunistically in accordance with a wide ranging foraging strategy. However, the consistent occurrence of cryptic and hidden prey indicates that active search foraging is also utilised. No evidence for ambush predation was found and, unlike many other small skinks, few arboreal or aerial prey are included in the diet, even though the habitat is rock scree and woodland where such prey abound. No evidence for any in a specific partitioning of diet based on kind or size of prey was obtained although a slight, but significant, correlation exists between maximum prey size and lizard size.
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