ORCID Profile
0000-0001-5338-7454
Current Organisation
University of Wollongong
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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)
Life Histories | Animal Physiological Ecology | Ecology | Behavioural Ecology | Ecological Physiology | Evolutionary Biology
ANZSRC Socio-Economic Objective (SEO)
Expanding Knowledge in the Biological Sciences | Effects of Climate Change and Variability on Australia (excl. Social Impacts) | Mountain and High Country Flora, Fauna and Biodiversity | Climate and Climate Change not elsewhere classified |
Related Links
Publications
Not just a chastity belt: the functional significance of mating plugs in garter snakes, revisited
Publisher: Oxford University Press (OUP)
Date: 23-04-2013
DOI: 10.1111/BIJ.12089
Sexual conflict over mating in red-sided garter snakes (Thamnophis sirtalis) as indicated by experimental manipulation of genitalia
Publisher: The Royal Society
Date: 07-01-2014
Abstract: Sexual conflict over mating can result in sex-specific morphologies and behaviours that allow each sex to exert control over the outcome of reproduction. Genital traits, in particular, are often directly involved in conflict interactions. Via genital manipulation, we experimentally investigated whether genital traits in red-sided garter snakes influence copulation duration and formation of a copulatory plug. The hemipenes of male red-sided garter snakes have a large basal spine that inserts into the female cloaca during mating. We ablated the spine and found that males were still capable of copulation but copulation duration was much shorter and copulatory plugs were smaller than those produced by intact males. We also anaesthetized the female cloacal region and found that anaesthetized females copulated longer than control females, suggesting that female cloacal and vaginal contractions play a role in controlling copulation duration. Both results, combined with known aspects of the breeding biology of red-sided garter snakes, strongly support the idea that sexual conflict is involved in mating interactions in this species. Our results demonstrate the complex interactions among male and female traits generated by coevolutionary processes in a wild population. Such complexity highlights the importance of simultaneous examination of male and female traits.
Female behaviour and the interaction of male and female genital traits mediate sperm transfer during mating
Publisher: Wiley
Date: 11-02-2016
DOI: 10.1111/JEB.12836
Abstract: Natural selection and post-copulatory sexual selection, including sexual conflict, contribute to genital ersification. Fundamental first steps in understanding how these processes shape the evolution of specific genital traits are to determine their function experimentally and to understand the interactions between female and male genitalia during copulation. Our experimental manipulations of male and female genitalia in red-sided garter snakes (Thamnophis sirtalis parietalis) reveal that copulation duration and copulatory plug deposition, as well as total and oviductal/vaginal sperm counts, are influenced by the interaction between male and female genital traits and female behaviour during copulation. By mating females with anesthetized cloacae to males with spine-ablated hemipenes using a fully factorial design, we identified significant female-male copulatory trait interactions and found that females prevent sperm from entering their oviducts by contracting their vaginal pouch. Furthermore, these muscular contractions limit copulatory plug size, whereas the basal spine of the male hemipene aids in sperm and plug transfer. Our results are consistent with a role of sexual conflict in mating interactions and highlight the evolutionary importance of female resistance to reproductive outcomes.
Evaluation of Drug Resistance Before and After Biofilm Formation of Bacteria Causing Wound Infection and Detection of Their Protease Activity
Publisher: Briefland
Date: 18-05-2021
DOI: 10.5812/IJI.108247
Abstract: Background: Wound infection is a highly common problem in hospital settings, where microbes are often resistant and difficult to treat due to rapid exposure to antibiotics. While treating wound infection, bacteria often enter the deep tissue as therapy needs long exposure time, bacteria have sufficient time to develop biofilm, which makes them much more resistant to antibiotics. Objectives: The current study was performed to identify wound-infecting bacteria and determine their protease production activity. Methods: The ability to produce biofilm was evaluated by the Congo red agar and tube methods. Antibiotic resistance pattern was assessed before and after biofilm formation to detect the changes in resistance due to biofilm formation. Results: We identified Pseudomonas aeruginosa, Proteus mirabilis, Proteus vulgaris, Corynebacterium xerosis, Alcaligenes faecalis, Bacillus cereus, Escherichia coli, Acinetobacter spp., Klebsiella pneumoniae, Staphylococcus spp., Shigella spp., and Salmonella spp. in 20 wound s les, among which about 10 isolates were found to be biofilm producers. Almost all the biofilm producers showed complete resistance or a much smaller inhibition zone. Conclusions: Pathogenic bacteria can be more difficult to eradicate by antibiotic treatment if they are able to produce biofilm thus, it is essential to prevent biofilm formation.
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
Sex‐ And tissue‐specific differences in telomere length in a reptile
Publisher: Wiley
Date: 22-05-2019
DOI: 10.1002/ECE3.5164
Dehydrated males are less likely to dive into the mating pool
Publisher: Oxford University Press (OUP)
Date: 31-12-2021
Abstract: The hydration state of animals vying for reproductive success may have implications for the tempo and mode of sexual selection, which may be salient in populations that experience increasing environmental fluctuations in water availability. Using red-sided garter snakes as a model system, we tested the effect of water supplementation on courtship, mating behavior, and copulatory plug (CP) production during a drought year. Over 3 days of mating trials, water-supplemented males (WET males, n = 45) outperformed a control group that was not supplemented with water (DRY males, n = 45). Over 70% of WET males mated but just 33% of DRY males did so. As a group, WET males mated 79 times versus 28 times by DRY males. On the last day of mating trials, over 70% of WET males were still courting, with 19 of them mating, whereas less than 25% of DRY males were courting and only one mated. CP deposition accounted for 4–6% of the mass lost by mating males, but hydration did not affect CP mass or water content. These findings suggest that, in years of low water availability, the number of courting males and the intensity of their courtship declines, thereby affecting sexual selection and conflict, at least within that year.
Size dependence in non-sperm ejaculate production is reflected in daily energy expenditure and resting metabolic rate
Publisher: The Company of Biologists
Date: 05-2015
DOI: 10.1242/JEB.120402
Abstract: The non-sperm components of an ejaculate, such as copulatory plugs, can be essential to male reproductive success. But the costs of these ejaculate components are often considered trivial. In polyandrous species, males are predicted to increase energy allocation to the production of non-sperm components, but this allocation is often condition dependent and the energetic costs of their production have never been quantified. Red-sided garter snakes (Thamnophis sirtalis parietalis) are an excellent model with which to quantify the energetic costs of non-sperm components of the ejaculate as they exhibit a dissociated reproductive pattern in which sperm production is temporally disjunct from copulatory plug production, mating and plug deposition. We estimated the daily energy expenditure and resting metabolic rate of males after courtship and mating, and used bomb calorimetry to estimate the energy content of copulatory plugs. We found that both daily energy expenditure and resting metabolic rate were significantly higher in small mating males than in courting males, and a single copulatory plug without sperm constitutes 5–18% of daily energy expenditure. To our knowledge, this is the first study to quantify the energetic expense of size-dependent ejaculate strategies in any species.
Covariation in superoxide, sperm telomere length and sperm velocity in a polymorphic reptile
Publisher: Springer Science and Business Media LLC
Date: 06-2020
The evolution and physiology of male pregnancy in syngnathid fishes
Publisher: Wiley
Date: 05-05-2020
DOI: 10.1111/BRV.12607
Size dependence in non-sperm ejaculate production is reflected in daily energy expenditure and resting metabolic rate
Publisher: The Company of Biologists
Date: 06-2015
DOI: 10.1242/JEB.125575
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.
Vitellogenin offsets oxidative costs of reproduction in female painted dragon lizards
Publisher: The Company of Biologists
Date: 2020
DOI: 10.1242/JEB.221630
Abstract: Vitellogenesis (“yolking” of follicles) is a bioenergetically costly stage of reproduction requiring enlargement of the liver to produce vitellogenin (VTG) yolk precursor proteins, which are transported and deposited at the ovary. VTG may, however, serve non-nutritive antioxidant functions, a hypothesis supported by empirical work on aging and other life-history transitions in several taxa. We test this hypothesis in female painted dragon lizards (Ctenophorus pictus) by examining covariation in VTG with the ovarian cycle, and relative to reactive oxygen species (ROS) including baseline superoxide (bSO). Plasma VTG decreased prior to ovulation, when VTG is deposited into follicles. VTG, however, remained elevated post-ovulation when no longer necessary for yolk provisioning and was unrelated to reproductive investment. Instead, VTG was strongly and positively predicted by prior bSO. ROS, in turn, was negatively predicted by prior VTG, while simultaneously s led VTG was a positive predictor. These findings are consistent with the hypothesis that VTG functions as an antioxidant to counteract oxidative stress associated with vitellogenesis. The relationship between bSO and VTG was strongest in post-ovulatory females, indicating its function may be largely antioxidant at this time. In conclusion, VTG may be under selection to offset oxidative costs of reproduction in egg-producing species.
Exercise training in a color-polymorphic lizard reveals differential effects of mating tactics and color morphs on telomere, body condition and growth dynamics
Publisher: Cold Spring Harbor Laboratory
Date: 24-12-2020
DOI: 10.1101/2020.12.23.424255
Abstract: Alternative reproductive tactics (ARTs) are correlated suites of sexually selected traits that are likely to impose differential physiological costs on different in iduals. While some level of activity might be beneficial, animals living in the wild are often working at the margins of their resources and performance limits. In iduals using ARTs may have ergent capacities for activity, and when pushed beyond their capacity, they may experience condition loss, oxidative stress, and molecular damage that must be repaired with limited resources. We used the Australian painted dragon lizard that exhibits color-polymorphims with corresponding alternative reproductive tactics (ARTs) as a model to experimentally test the effect of exercise on body condition, growth, reactive oxygen species (ROS), and telomere dynamics—a potential marker of stress and aging and a correlate of longevity. For most males, ROS tended to be lower with greater exercise however, males with yellow throat patches—or bibs— had higher ROS than non-bibbed males. At the highest level of exercise, bibbed males exhibited telomere loss, while non-bibbed males gained telomere length the opposite pattern was observed in the no-exercise controls. Growth was positively related to food intake but negatively correlated with telomere length at the end of the experiment. Body condition was not related to food intake but was positively correlated with increases in telomere length. These results, along with our previous work, suggest that aggressive bibbed males suffer physiological costs that may reduce longevity.
Long‐term effects of superoxide and DNA repair on lizard telomeres
Publisher: Wiley
Date: 12-2018
DOI: 10.1111/MEC.14913
Abstract: Telomeres are the non-coding protein-nucleotide "caps" at chromosome ends that contribute to chromosomal stability by protecting the coding parts of the linear DNA from shortening at cell ision, and from erosion by reactive molecules. Recently, there has been some controversy between molecular and cell biologists, on the one hand, and evolutionary ecologists on the other, regarding whether reactive molecules erode telomeres during oxidative stress. Many studies of biochemistry and medicine have verified these relationships in cell culture, but other researchers have failed to find such effects in free-living vertebrates. Here, we use a novel approach to measure free radicals (superoxide), mitochondrial "content" (a combined measure of mitochondrial number and size in cells), telomere length and DNA damage at two primary time points during the mating season of an annual lizard species (Ctenophorus pictus). Superoxide levels early in the mating season vary widely and elevated levels predict shorter telomeres both at that time as well as several months later. These effects are likely driven by mitochondrial content, which significantly impacts late season superoxide (cells with more mitochondria have more superoxide), but superoxide effects on telomeres are counteracted by DNA repair as revealed by 8-hydroxy-2'-deoxyguanosine assays. We conclude that reactive oxygen species and DNA repair are fundamental for both short- and long-term regulation of lizard telomere length with pronounced effects of early season cellular stress detectable on telomere length near lizard death.
The relationship of body condition, superoxide dismutase, and superoxide with sperm performance
Publisher: Oxford University Press (OUP)
Date: 11-06-2019
Abstract: Sperm competition theory predicts a negative correlation between somatic investment and traits that aid in pre- and postcopulatory sexual selection. Sperm performance is critical for postcopulatory success but sperm are susceptible to damage by free radicals such as superoxide radicals generated during mitochondrial respiration (mtSOx). Males can ameliorate damage to spermatozoa by investing in the production of antioxidants, like superoxide dismutase (SOD), which may act as a mechanistic link to pre- and postcopulatory trade-offs. Some male Australian, color-polymorphic painted dragon lizards (Ctenophorus pictus) possess a yellow throat patch (bib) that females prefer over nonbibbed males and are also more likely to win male–male contests indicating that males with bibs may be better at monopolizing females. We tested whether the sperm performance in nonbibbed males was superior to that of bibbed males. We show that overall sperm performance was not different between the bib-morphs, however, higher mtSOx levels were negatively correlated with sperm performance in bibbed males, but not of nonbibbed males. Blood cell mtSOx levels are negatively correlated with SOD activity in the plasma in all males early in the breeding season but SOD was lower in bibbed males. Nonbibbed males maintain a positive correlation between body condition and SOD activity over time while bibbed males do not. Together, these data suggest physiological associations between body condition, SOD activity, and sperm performance are linked to the expression of a yellow gular patch, which may be related to intrinsic differences in the metabolism of bibbed versus nonbibbed males.
Sperm competition in squamate reptiles
Publisher: The Royal Society
Date: 19-10-2020
Abstract: Multiple paternity is ubiquitous within the polyphyletic group called ‘reptiles', especially within the lizards and snakes. Therefore, the probability of sperm competition occurring, and being intense, is high. Squamates exhibit a ersity of tactics to ensure fertilization success in the face of sperm competition. The duration of female sperm storage, which can be many months and even years in some species, remains an enigma. Here, we emphasize some mechanisms that might affect patterns of paternity, the source and function of ejaculates and features of the female reproductive tract that may aid in long-term sperm storage. In doing so, we present a new analysis of the relationship between sperm size, the strength of sperm competition and the duration of female sperm storage. Lizards and snakes are a erse group that has provided many excellent models for the study of an array of life-history strategies. However, when it comes to postcopulatory sexual selection, there is much left to discover. This article is part of the theme issue ‘Fifty years of sperm competition'.
Individual variation in thermal plasticity and its impact on mass‐scaling
Publisher: Wiley
Date: 29-04-2021
DOI: 10.1111/OIK.08122
Abstract: Physiological processes vary widely across in iduals and can influence how in iduals respond to environmental change. Repeatability in how metabolic rate changes across temperatures (i.e. metabolic thermal plasticity) can influence mass‐scaling exponents in different thermal environments. Moreover, repeatable plastic responses are necessary for reaction norms to respond to selective forces which is important for populations living in fluctuating environments. Nonetheless, only a small number of studies have explicitly quantified repeatability in metabolic plasticity, and fewer have explored how it can impact mass‐scaling. We repeatedly measured standard metabolic rate of n = 42 delicate skinks L ropholis delicata at six temperatures over the course of four months ( N [observations] = 4952). Using hierarchical statistical techniques, we accounted for multi‐level variation and measurement error in our data in order to obtain more precise estimates of reaction norm repeatability and mass‐scaling exponents at different acute temperatures. Our results show that in idual differences in metabolic thermal plasticity were somewhat consistent over time (R slope = 0.25, 95% CI = 2.48 × 10 −8 – 0.67), however estimates were associated with a large degree of error. After accounting for measurement error, which decreased steadily with temperature, we show that among in idual variance remained consistent across all temperatures. Congruently, temperature specific repeatability of average metabolic rate was stable across temperatures. Cross‐temperature correlations were positive but were not uniform across the reaction norm. After taking into account multiple sources of variation, our estimates for mass‐scaling did not change with temperature and were in line with published values for snakes and lizards. This implies that repeatable plastic responses may promote thermal stability of scaling exponents. Our work contributes to understanding how energy expenditure scales with abiotic and biotic factors and the capacity for reaction norms to respond to selection.
Patterns of sperm use in two populations of Red-sided Garter Snake (Thamnophis sirtalis parietalis) with long-term female sperm storage
Publisher: Canadian Science Publishing
Date: 2014
Abstract: Long-term sperm storage may contribute to postcopulatory sexual selection because it enhances the commingling of sperm from different males within the female reproductive tract, which is the prerequisite for sperm competition. Long-term sperm storage and multiple paternity has been documented in snakes, but the identity of the last potential father is usually unknown in studies demonstrating multiple paternity. Here we present the first study in Red-sided Garter Snakes (Thamnophis sirtalis parietalis (Say in James, 1832)) to use experimental population crosses to assess stored sperm usage, mate-order effects, and the potential for interpopulational gametic isolation. We found a high rate of multiple paternity indicative of ubiquitous long-term sperm storage in this system, and observed last-male sperm precedence in all families (n = 66). Postzygotic isolation was absent, and we observed only a weak asymmetry in pattern of sperm precedence in our population crosses.
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.
Experimental heatwaves negatively impact sperm quality in the zebra finch
Publisher: The Royal Society
Date: 17-01-2018
Abstract: For sexually reproducing species, functionally competent sperm are critical to reproduction. While high atmospheric temperatures are known to influence the timing of breeding, incubation and reproductive success in birds, the effect of temperature on sperm quality remains largely unexplored. Here, we experimentally investigated the impact of ecologically relevant extreme temperatures on cloacal temperature and sperm morphology and motility in zebra finches Taeniopygia guttata . We periodically s led males exposed to 30°C or 40°C temperatures daily for 14 consecutive days. Following a 12-day (23°C) recovery period, birds were again exposed to heat, but under the alternate treatment (e.g. birds initially exposed to 40°C were exposed to 30°C). Elevated temperatures led to an increase in cloacal temperature and a reduction in the proportion of sperm with normal morphology these effects were most notable under 40°C conditions, and were influenced by the duration of heat exposure and prior exposure to high temperature. Our findings highlight the potential role of temperature in determining male fertility in birds, and perhaps also in constraining the timing of avian breeding. Given the increased frequency of heatwaves in a warming world, our results suggest the need for further work on climatic influences on sperm quality and male fertility.
Ageing and the cost of maintaining coloration in the Australian painted dragon
Publisher: The Royal Society
Date: 07-2016
Abstract: There is now good evidence in several taxa that animal coloration positively reflects an in idual's antioxidant capacity. However, even though telomeres, a marker of ageing, are known to be vulnerable to reactive oxygen species (ROS) attacks, no studies have ever assessed whether colour fading reflects the rate of biological ageing in any taxa. Here, we measured colour fading, telomere erosion (a measure of biological ageing) and ROS levels in painted dragons. We show that in iduals that were better at maintaining their coloration during the three months of the study suffered a higher cost in terms of telomere erosion, but overall ROS levels measured at the start of the study were not significantly related to colour maintenance and telomere shortening. We therefore suggest that colour maintenance is a costly phenomenon in terms of telomere erosion, and that overall ROS levels do not seem to be a crucial component linking ornamental coloration and telomere erosion in our study system.
Intrapopulational variation of ejaculate traits and sperm depletion in red‐sided garter snakes
Publisher: Wiley
Date: 16-01-2014
DOI: 10.1111/JZO.12092
Invited review: Thermal effects on oxidative stress in vertebrate ectotherms
Publisher: Elsevier BV
Date: 2022
DOI: 10.1016/J.CBPA.2021.111082
Abstract: Human-induced climate change is occurring rapidly. Ectothermic organisms are particularly vulnerable to these temperature changes due to their reliance on environmental temperature. The extent of ectothermic thermal adaptation and plasticity in the literature is well documented however, the role of oxidative stress in these processes needs more attention. Oxidative stress occurs when reactive oxygen species, generated mainly through aerobic respiration, overwhelm antioxidant defences and damage crucial biomolecules. The effects of oxidative damage include the alteration of life-history traits and reductions in whole-organism fitness. Here we review the literature addressing experimental temperature effects on oxidative stress in vertebrate ectotherms. Acute and acclimation temperature treatments produce distinctly different results and highlight the role of phylogeny and thermal adaptation in shaping oxidative stress responses. Acute treatments on organisms adapted to stable environments generally produced significant oxidative stress responses, whilst organisms adapted to variable conditions exhibited capacity to cope with temperature changes and mitigate oxidative stress. In acclimation treatments, the temperature treatments higher than optimal temperatures tended to produce significantly less oxidative stress than lower temperatures in reptiles, whilst in some eurythermal fish species, no oxidative stress response was observed. These results highlight the importance of phylogeny and adaptation to past environmental conditions for temperature-dependent oxidative stress responses. We conclude with recommendations on experimental procedures to investigate these phenomena with reference to thermal plasticity, adaptation and biogeographic variation that provide the most significant benefits to adaptable populations. These results have potential conservation ramifications as they may shed light on the physiological effects of temperature alterations in some vertebrate ectotherms.
Correlated evolution of sexually selected traits: interspecific variation in ejaculates, sperm morphology, copulatory mate guarding, and body size in two sympatric species of garter snakes
Publisher: Springer Science and Business Media LLC
Date: 30-11-2017
Age-related sex differences in body condition and telomere dynamics of red-sided garter snakes
Publisher: The Royal Society
Date: 05-04-2017
Abstract: Life-history strategies vary dramatically between the sexes, which may drive ergence in sex-specific senescence and mortality rates. Telomeres are tandem nucleotide repeats that protect the ends of chromosomes from erosion during cell ision. Telomeres have been implicated in senescence and mortality because they tend to shorten with stress, growth and age. We investigated age-specific telomere length in female and male red-sided garter snakes, Thamnophis sirtalis parietalis . We hypothesized that age-specific telomere length would differ between males and females given their ergent reproductive strategies. Male garter snakes emerge from hibernation with high levels of corticosterone, which facilitates energy mobilization to fuel mate-searching, courtship and mating behaviours during a two to four week aphagous breeding period at the den site. Conversely, females remain at the dens for only about 4 days and seem to invest more energy in growth and cellular maintenance, as they usually reproduce biennially. As male investment in reproduction involves a yearly bout of physiologically stressful activities, while females prioritize self-maintenance, we predicted male snakes would experience more age-specific telomere loss than females. We investigated this prediction using skeletochronology to determine the ages of in iduals and qPCR to determine telomere length in a cross-sectional study. For both sexes, telomere length was positively related to body condition. Telomere length decreased with age in male garter snakes, but remained stable in female snakes. There was no correlation between telomere length and growth in either sex, suggesting that our results are a consequence of ergent selection on life histories of males and females. Different selection on the sexes may be the physiological consequence of the sexual dimorphism and mating system dynamics displayed by this species.
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'.
Conditional Handicaps in Exuberant Lizards: Bright Color in Aggressive Males Is Correlated with High Levels of Free Radicals
Publisher: Frontiers Media SA
Date: 02-2017
Sexual coloration and sperm performance in the Australian painted dragon lizard, Ctenophorus pictus
Publisher: Wiley
Date: 29-05-2017
DOI: 10.1111/JEB.13092
Abstract: Theory predicts trade-offs between pre- and post-copulatory sexually selected traits. This relationship may be mediated by the degree to which males are able to monopolize access to females, as this will place an upper limit on the strength of post-copulatory selection. Furthermore, traits that aid in mate monopolization may be costly to maintain and may limit investment in post-copulatory traits, such as sperm performance. Australian painted dragons are polymorphic for the presence or absence of a yellow gular patch ('bibs'), which may aid them to monopolize access to females. Previous work has shown that there are physiological costs of carrying this bib (greater loss of body condition in the wild). Here, we show that male painted dragons use this bright yellow bib as both an inter- and intrasexual signal, and we assess whether this signal is traded off against sperm performance within the same in iduals. We found no relationship between aspects of bib colour and sperm swimming velocity or percentage of motile sperm and suggest that the bib polymorphism may be maintained by complex interactions between physiological or life-history traits including other sperm or ejaculate traits and environmental influences.
Telomere dynamics in a lizard with morph‐specific reproductive investment and self‐maintenance
Publisher: Wiley
Date: 07-06-2017
DOI: 10.1002/ECE3.2712
Sperm telomere length correlates with blood telomeres and body size in red‐sided garter snakes, Thamnophis sirtalis parietalis
Publisher: Wiley
Date: 16-05-2020
DOI: 10.1111/JZO.12789
The role of oxidative stress in postcopulatory selection
Publisher: The Royal Society
Date: 19-10-2020
Abstract: Two decades ago, von Schantz et al . (von Schantz T, Bensch S, Grahn M, Hasselquist D, Wittzell H. 1999 Good genes, oxidative stress and condition-dependent sexual signals. Proc. R. Soc. B 266, 1–12. ( doi:10.1098/rspb.1999.0597 )) united oxidative stress (OS) biology with sexual selection and life-history theory. This set the scene for analysis of how evolutionary trade-offs may be mediated by the increase in reactive molecules resulting from metabolic processes at reproduction. Despite 30 years of research on OS effects on infertility in humans, one research area that has been left behind in this integration of evolution and OS biology is postcopulatory sexual selection—this integration is long overdue. We review the basic mechanisms in OS biology, why mitochondria are the primary source of ROS and ATP production during oxidative metabolism, and why sperm, and its performance, is uniquely susceptible to OS. We also review how postcopulatory processes select for antioxidation in seminal fluids to counter OS and the implications of the net outcome of these processes on sperm damage, sperm storage, and female and oocyte manipulation of sperm metabolism and repair of DNA to enhance offspring fitness. This article is part of the theme issue ‘Fifty years of sperm competition’.
Using whole-group metabolic rate and behaviour to assess the energetics of courtship in red-sided garter snakes
Publisher: Elsevier BV
Date: 08-2017
At the invasion front, male cane toads (Rhinella marina) have smaller testes
Publisher: The Royal Society
Date: 07-2019
Abstract: As a colonizing species expands its range, in iduals at the invasion front experience different evolutionary pressures than do those at the range-core. For ex le, low densities at the edge of the range mean that males should rarely experience intense sperm competition from rivals and investment into reproduction may trade-off with adaptations for more rapid dispersal. Both of these processes are predicted to favour a reduction in testis size at the invasion front. To explore effects of invasion stage in Australian cane toads ( Rhinella marina ), we collected and dissected 214 adult males from three regions: one in the species' range-core (northeastern Australia), and two from invasion fronts (one in northwestern Australia and one in southeastern Australia). Despite the brief duration of separation between toads in these areas (approx. 85 years), testis masses averaged greater than 30% higher (as a proportion of body mass) in range-core males than in conspecifics s led from either vanguard of the invasion. Previous work has documented low reproductive frequencies in female cane toads at the invasion front also, consistent with the hypothesis that evolutionary and ecological pressures unleashed by an invasion can favour relatively low resource allocation to reproduction in both sexes.
Factors influencing paternity in multiply mated female red-sided garter snakes and the persistent use of sperm stored over winter
Publisher: Springer Science and Business Media LLC
Date: 06-2014
Morph-specific metabolic rate and the timing of reproductive senescence in a color polymorphic dragon
Publisher: Wiley
Date: 08-2017
DOI: 10.1002/JEZ.2118
Abstract: Polymorphism has fascinated biologists for over a century because morphs persist within populations through evolutionary time in spite of showing disparate behavioral and physiological phenotypes any one morph should go to fixation with the slightest fitness advantage over the others. Surely there must be trade-offs that balance selection on them. The polychromatic morphs of the Australian painted dragon lizard, Ctenophorus pictus, are one such system. The male color morphs of painted dragons have different physiological and behavioral traits including reproductive tactics, hormone levels, and the rate of body condition loss through the reproductive season. Due to their differences in physiology and reproductive tactics, we tested the hypotheses that male morphs would differ in resting metabolic rates (RMRs) and that the morphs' RMR would decline at different rates through the mating season. We found that bib-morphs (yellow gular patch) differ in RMR with bibbed (more aggressive) males having consistently higher RMR than non-bibbed males. Furthermore, we show that male dragons experience a decline in RMR as they age from reproductively active to inactive. We also found that the RMR of bibbed males has higher repeatability than non-bibbed males. Our results reinforce previous hypotheses about the morph-specific costs of bearing a gular patch in painted dragons.
Polyandry and Female Postcopulatory Choice
Publisher: Elsevier
Date: 2016
Postcopulatory sexual selection as a driver of sex- and population-specific kidney mass in garter snakes?
Publisher: Oxford University Press (OUP)
Date: 23-03-2021
DOI: 10.1093/BIOLINNEAN/BLAB019
Abstract: In lizards and snakes, the kidneys produce seminal fluid in addition to having osmoregulatory functions. Therefore, in response to polyandry, kidney mass should be under selection regimes such as those influencing testes. Male red-sided garter snakes deposit a kidney-derived copulatory plug that functions in sperm competition. We first tested for intersexual differences in kidney mass and allometry in one population and found that males had kidneys twice as heavy as those of females, consistent with stronger selection on male kidney mass. Previous studies have shown that male size enhances mating success in one-on-one competition prevalent in small mating aggregations. We then examined the relationship between body size, kidney mass and testes mass in two populations with low (LD) and high (HD) mating aggregation densities. Males from the HD population had heavier testes and heavier kidneys compared with males from the LD population HD males were also smaller in body size. Our results suggest that the strength of sexual selection, and possibly the balance between pre- and postcopulatory selection, varies in response to population size or density. However, more replication is needed to confirm the generality of these results within red-sided garter snakes and other squamate reptiles.
Exercise training has morph-specific effects on telomere, body condition and growth dynamics in a color-polymorphic lizard
Publisher: The Company of Biologists
Date: 05-2021
DOI: 10.1242/JEB.242164
Abstract: Alternative reproductive tactics (ARTs) are correlated suites of sexually selected traits that are likely to impose differential physiological costs on different in iduals. While moderate activity might be beneficial, animals living in the wild often work at the margins of their resources and performance limits. In iduals using ARTs may have ergent capacities for activity. When pushed beyond their respective capacities, they may experience condition loss, oxidative stress, and molecular damage that must be repaired with limited resources. We used the Australian painted dragon lizard that exhibits color polymorphism as a model to experimentally test the effect of exercise on body condition, growth, reactive oxygen species (ROS) and telomere dynamics – a potential marker of stress and aging and a correlate of longevity. For most males, ROS levels tended to be lower with greater exercise however, males with yellow throat patches – or bibs – had higher ROS levels than non-bibbed males. At the highest level of exercise, bibbed males exhibited telomere loss, while non-bibbed males gained telomere length the opposite pattern was observed in the no-exercise controls. Growth was positively related to food intake but negatively correlated with telomere length at the end of the experiment. Body condition was not related to food intake but was positively correlated with increases in telomere length. These results, along with our previous work, suggest that aggressive – territory holding – bibbed males suffer physiological costs that may reduce longevity compared with non-bibbed males with superior postcopulatory traits.
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Discovery Projects - Grant ID: DP210101152
Start Date: 08-2021
End Date: 08-2024
Amount: $405,960.00
Funder: Australian Research Council
View Funded ActivityDiscovery Projects - Grant ID: DP220102928
Start Date: 11-2022
End Date: 10-2025
Amount: $468,000.00
Funder: Australian Research Council
View Funded Activity