ORCID Profile
0000-0003-3362-1412
Current Organisation
Flinders University
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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 | Biological Adaptation | Ecology And Evolution Not Elsewhere Classified | Biological Physics | Animal Physiology - Biophysics | Sociobiology And Behavioural Ecology | Behavioural Ecology | Optical properties of materials | Evolutionary biology | Ecology | Physical Chemistry of Materials | Optical Properties of Materials | Macromolecular and Materials Chemistry | Zoology Not Elsewhere Classified | Plant Biology | Structural Chemistry and Spectroscopy | Speciation and Extinction | Population, Ecological and Evolutionary Genetics | Biological physics | Infectious Agents | Plant Cell and Molecular Biology | Animal Cell and Molecular Biology | Genomics | Phylogeny and Comparative Analysis | Population And Ecological Genetics | Biological adaptation | Ecological Physiology
ANZSRC Socio-Economic Objective (SEO)
Expanding Knowledge in the Biological Sciences | Biological sciences | Environmentally Sustainable Plant Production not elsewhere classified | Living resources (flora and fauna) | Flora, Fauna and Biodiversity of environments not elsewhere classified | Management of Water Consumption by Plant Production | Control of Pests, Diseases and Exotic Species not elsewhere classified | Expanding Knowledge in the Chemical Sciences | Expanding Knowledge in the Physical Sciences |
Related Links
Publications
Climate is a strong predictor of near-infrared reflectance but a poor predictor of colour in butterflies
Publisher: The Royal Society
Date: 13-03-2019
Abstract: Colour variation across climatic gradients is a common ecogeographical pattern yet there is long-standing contention over underlying causes, particularly selection for thermal benefits. We tested the evolutionary association between climate gradients and reflectance of near-infrared (NIR) wavelengths, which influence heat gain but are not visible to animals. We measured ultraviolet (UVA), visible (Vis) and NIR reflectance from calibrated images of 372 butterfly specimens from 60 populations (49 species, five families) spanning the Australian continent. Consistent with selection for thermal benefits, the association between climate and reflectance was stronger for NIR than UVA–Vis wavelengths. Furthermore, climate predicted reflectance of the thorax and basal wing, which are critical to thermoregulation but it did not predict reflectance of the entire wing, which has a variable role in thermoregulation depending on basking behaviour. These results provide evidence that selection for thermal benefits has shaped the reflectance properties of butterflies.
Rapid beard darkening predicts contest outcome, not copulation success, in bearded dragon lizards
Publisher: Elsevier BV
Date: 12-2020
How sexual and natural selection shape sexual size dimorphism: Evidence from multiple evolutionary scales
Publisher: Wiley
Date: 03-05-2019
Shouting the odds: vocalization signals status in a lizard
Publisher: Springer Science and Business Media LLC
Date: 22-12-2006
Variation in Phenotype, Parasite Load and Male Competitive Ability across a Cryptic Hybrid Zone
Publisher: Public Library of Science (PLoS)
Date: 25-05-2009
High contrast yellow mosaic patterns are prey attractants for orb‐weaving spiders
Publisher: Wiley
Date: 11-02-2020
Ultraviolet signals ultra-aggression in a lizard
Publisher: Elsevier BV
Date: 08-2006
Invasive chameleons released from predation display more conspicuous colors
Publisher: American Association for the Advancement of Science (AAAS)
Date: 13-05-2022
Abstract: Conspicuous social and sexual signals are predicted to experience pronounced character release when natural selection via predation is relaxed. However, we have few good ex les of this phenomenon in the wild and none in species with dynamic color change. Here, we show that Jackson’s chameleons inadvertently introduced from Kenya to Hawaii (Oahu), where there are no coevolved, native lizard predators, experienced pronounced character release of color signals. Hawaiian chameleons displayed more conspicuous social color signals than Kenyan chameleons during male contests and courtship, were less cryptic in response to bird and snake predators, and showed greater change between display and antipredator color states. Hawaiian chameleon display colors were also more conspicuous in their local than ancestral habitats, consistent with local adaptation of social signals. These results demonstrate that relaxed predation pressure can result in character release of dynamic social signals in introduced species experiencing strong sexual selection.
From cryptic to colorful: Evolutionary decoupling of larval and adult color in butterflies
Publisher: Oxford University Press (OUP)
Date: 02-2020
DOI: 10.1002/EVL3.149
Abstract: Many animals undergo complete metamorphosis, where larval forms change abruptly in adulthood. Color change during ontogeny is common, but there is little understanding of evolutionary patterns in these changes. Here, we use data on larval and adult color for 246 butterfly species (61% of all species in Australia) to test whether the evolution of color is coupled between life stages. We show that adults are more variable in color across species than caterpillars and that male adult color has lower phylogenetic signal. These results suggest that sexual selection is driving color ersity in male adult butterflies at a broad scale. Moreover, color similarities between species at the larval stage do not predict color similarities at the adult stage, indicating that color evolution is decoupled between young and adult forms. Most species transition from cryptic coloration as caterpillars to conspicuous coloration as adults, but even species with conspicuous caterpillars change to different conspicuous colors as adults. The use of high-contrast coloration is correlated with body size in caterpillars but not adults. Taken together, our results suggest a change in the relative importance of different selective pressures at different life stages, resulting in the evolutionary decoupling of coloration through ontogeny.
Multiple fitness benefits of polyandry in a cephalopod
Publisher: Public Library of Science (PLoS)
Date: 16-05-2012
A complex history of introgression and vicariance in a threatened montane skink (Pseudemoia cryodroma) across an Australian sky island system
Publisher: Springer Science and Business Media LLC
Date: 23-02-2017
The predation cost of female resistance
Publisher: Oxford University Press (OUP)
Date: 2010
Environmental gradients predict the ratio of environmentally acquired carotenoids to self‐synthesised pteridine pigments
Publisher: Wiley
Date: 04-08-2021
DOI: 10.1111/ELE.13850
Abstract: Carotenoids are important pigments producing integument colouration however, their dietary availability may be limited in some environments. Many species produce yellow to red hues using a combination of carotenoids and self‐synthesised pteridine pigments. A compelling hypothesis is that pteridines replace carotenoids in environments where carotenoid availability is limited. To test this hypothesis, we quantified concentrations of five carotenoid and six pteridine pigments in multiple skin colours and in iduals from 27 species of agamid lizards. We show that environmental gradients predict the ratio of carotenoids to pteridines carotenoid concentrations are lower and pteridine concentrations higher in arid environments with low vegetation productivity. Both carotenoid and pteridine pigments were present in all species, but only pteridine concentrations explained colour variation among species and there were no correlations between carotenoid and pteridine pigments with a similar hue. These results suggest that in arid environments, where carotenoids are likely limited, species may compensate by synthesising more pteridines but do not necessarily replace carotenoids with pteridines of similar hue.
The ecological significance of time sense in animals
Publisher: Wiley
Date: 08-11-2021
DOI: 10.1111/BRV.12665
The contribution of structural-, psittacofulvin- and melanin-based colouration to sexual dichromatism in Australasian parrots
Publisher: Wiley
Date: 04-11-2011
DOI: 10.1111/J.1420-9101.2010.02166.X
Abstract: Colour ornamentation in animals is exceptionally erse, but some colours may provide better signals of in idual quality or more efficient visual stimuli and, thus, be more often used as sexual signals. This may depend on physiological costs, which depend on the mechanism of colour production (e.g. exogenously acquired colouration in passerine birds appears to be most sexually dichromatic). We studied sexual dichromatism in a s le of 27 Australasian parrot species with pigment- (melanin and psittacofulvin) and structural-based colouration, to test whether some of these types of colouration are more prominent in sexual ornamentation. Unlike passerines, in which long wavelength colouration (yellow to red) usually involves exogenous and costly carotenoid pigments, yellow to red colouration in parrots is based on endogenously synthesized psittacofulvin pigments. This allows us to assess whether costly exogenous pigments are necessary for these plumage colours to have a prominent role in sexual signalling. Structural blue colouration showed the largest and most consistent sexual dichromatism, both in area and perceptually relevant chromatic differences, indicating that it is often ornamental in parrots. By contrast, we found little evidence for consistent sexual dichromatism in melanin-based colouration. Unlike passerines, yellow to red colouration was not strongly sexually dichromatic: although the area of colouration was generally larger in males, colour differences between the sexes were on average imperceptible to parrots. This is consistent with the idea that the prominent yellow to red sexual dichromatism in passerines is related to the use of carotenoid pigments, rather than resulting from sensory bias for these colours.
Heating rates are more strongly influenced by near-infrared than visible reflectance in beetles
Publisher: The Company of Biologists
Date: 10-2021
DOI: 10.1242/JEB.242898
Abstract: Adaptations to control heat transfer through the integument are a key component of temperature regulation in animals. However, there remain significant gaps in our understanding of how different optical and morphological properties of the integument affect heating rates. To address these gaps, we examined the effect of reflectivity in both ultraviolet–visible and near-infrared wavelengths, surface rugosity (roughness), effective area (area subjected to illumination) and cuticle thickness on radiative heat gain in jewel beetles (Buprestidae). We measured heating rate using a solar simulator to mimic natural sunlight, a thermal chamber to control the effects of conduction and convection, and optical filters to isolate different wavelengths. We found that effective area and reflectivity predicted heating rate. The thermal effect of reflectivity was driven by variation in near-infrared rather than ultraviolet–visible reflectivity. By contrast, cuticle thickness and surface rugosity had no detectable effect. Our results provide empirical evidence that near-infrared reflectivity has an important effect on radiative heat gain. Modulating reflectance of near-infrared wavelengths of light may be a more widespread adaptation to control heat gain than previously appreciated.
Challenges and opportunities for innovation in bioinformed sustainable materials
Publisher: Springer Science and Business Media LLC
Date: 04-10-2023
Does the Lizard Platysaurus Broadleyi Aggregate Because of Social Factors?
Publisher: Society for the Study of Amphibians and Reptiles
Date: 09-2007
Cracks in the mirror hypothesis: High specularity does not reduce detection or predation risk
Publisher: Wiley
Date: 16-11-2022
Abstract: Some animals, including certain fish, beetles, spiders and Lepidoptera chrysalises, have such shiny or glossy surfaces that they appear almost mirror‐like. A compelling but unsubstantiated hypothesis is that a highly specular or mirror‐like appearance enhances survival by reflecting the surrounding environment and reducing detectability. We tested this hypothesis by asking human participants to wear a mobile eye‐tracking device and locate highly realistic mirror‐green and diffuse‐green replica beetles against a variety of backgrounds in a natural forest environment. We also tested whether a mirror‐like appearance enhances survival to wild predators by monitoring the survival of mirror‐green and diffuse‐green replica beetles in a forested habitat and an open habitat. Human participants showed no difference in the detection probability or detection latency of mirror versus diffuse replica beetles, indicating that mirror‐like appearance does not impair prey capture. The field predation experiment found no difference in survival between the mirror and diffuse replica beetles in forested environments. Similarly, there was no difference in survival when beetles were deployed in the open habitat where there is no background to reflect, indicating that predators detect and do not actively avoid mirror‐like beetles. Our results suggest that a mirror‐like appearance does not reduce attack by predators. Instead, highly specular, mirror‐like surfaces may have evolved for an alternate visual function or as a secondary consequence of selection for a non‐visual function, such as thermoregulation. A free Plain Language Summary can be found within the Supporting Information of this article.
Temperature-induced colour change varies seasonally in bearded dragon lizards
Publisher: Oxford University Press (OUP)
Date: 23-12-2017
Divergent male and female mate preferences do not explain incipient speciation between lizard lineages
Publisher: Oxford University Press (OUP)
Date: 12-03-2020
DOI: 10.1093/CZ/ZOAA010
Abstract: Diversification in sexual signals is often taken as evidence for the importance of sexual selection in speciation. However, in order for sexual selection to generate reproductive isolation between populations, both signals and mate preferences must erge together. Furthermore, assortative mating may result from multiple behavioral mechanisms, including female mate preferences, male mate preferences, and male–male competition yet their relative contributions are rarely evaluated. Here, we explored the role of mate preferences and male competitive ability as potential barriers to gene flow between 2 ergent lineages of the tawny dragon lizard, Ctenophorus decresii, which differ in male throat coloration. We found stronger behavioral barriers to pairings between southern lineage males and northern lineage females than between northern males and southern females, indicating incomplete and asymmetric behavioral isolating barriers. These results were driven by both male and female mate preferences rather than lineage differences in male competitive ability. Intrasexual selection is therefore unlikely to drive the outcome of secondary contact in C. decresii, despite its widely acknowledged importance in lizards. Our results are consistent with the emerging view that although both male and female mate preferences can erge alongside sexual signals, speciation is rarely driven by ergent sexual selection alone.
Has contemporary climate change played a role in population declines of the lizard Ctenophorus decresii from semi-arid Australia?
Publisher: Elsevier BV
Date: 12-2015
DOI: 10.1016/J.JTHERBIO.2014.12.001
Abstract: Whilst contemporary climatic changes are small in magnitude compared to those predicted for the coming decades, they have already been linked to species range shifts and local extinctions. Elucidating the drivers behind species' responses to contemporary climate change will better inform management strategies for vulnerable and pest species alike. A recent proposal to explain worldwide local extinctions in lizards is that increasing maximum temperatures have constrained lizard activity time in the breeding season beyond extinction thresholds. Here we document a significant population decline and potential local extinction at the warm (northern) range margin of the tawny dragon, Ctenophorus decresii, a rock-dwelling lizard from the Flinders Ranges in semi-arid Australia. We developed and tested a biophysical model of tawny dragon thermoregulatory behaviour and drove the model with daily weather data for the period 1990-2009 across the Flinders Ranges. Our results indicate that potential annual activity time has likely increased over this period throughout the historic range, with within-season declines only in the summer months at the northern range limit. However, populations that have declined since 2000 have also likely experienced higher active body temperatures and more stringent retreat-site requirements (deeper crevices) than have regions where the species remains common, during a period of declining rainfall. Our laboratory estimates of thermal preference in this species were insensitive to altered nutritional and hydric state. Thus it is possible that recent population declines are linked to desiccation stress driven by higher body temperatures and declining rainfall. Our study illustrates that simple indices of the impact of climate warming on animals, such as activity restriction, may in fact reflect a variety of potential mechanisms whose ultimate outcome will be contingent on other factors such as water and shelter availability.
Spermatophore consumption in a cephalopod
Publisher: The Royal Society
Date: 23-08-2013
Abstract: An in idual's gametes can represent a nourishing food source for a manipulative mate. Here, we provide evidence of ejaculate and sperm consumption in a cephalopod. Through labelling male spermatophores with 14 C radiolabel, we found that female squid, Sepiadarium austrinum , consumed the spermatophores of their partners and directed the nutrients received into both somatic maintenance and egg production. We further show that in this species—where fertilization occurs externally in the female's buccal cavity—sperm storage is short-term (less than 21 days). The combination of female spermatophore consumption and short-term external sperm storage has the potential to exert strong selection on male ejaculates and reproductive strategies.
Ornament size and colour as alternative strategies for effective communication in gliding lizards
Publisher: Wiley
Date: 27-06-2016
DOI: 10.1111/JEB.12908
Abstract: Sexual ornamentation needs to be conspicuous to be effective in attracting potential mates and defending territories and indeed, a multitude of ways exists to achieve this. Two principal mechanisms for increasing conspicuousness are to increase the ornament's colour or brightness contrast against the background and to increase the size of the ornament. We assessed the relationship between the colour and size of the dewlap, a large extendible throat-fan, across a range of species of gliding lizards (Agamidae genus Draco) from Malaysia and the Philippines. We found a negative relationship across species between colour contrast against the background and dewlap size in males, but not in females, suggesting that males of different species use increasing colour contrast and dewlap size as alternative strategies for effective communication. Male dewlap size also increases with increasing sexual size dimorphism, and dewlap colour and brightness contrast increase with increasing sexual dichromatism in colour and brightness, respectively, suggesting that sexual selection may act on both dewlap size and colour. We further found evidence that relative predation intensity, as measured from predator attacks on models placed in the field, may play a role in the choice of strategy (high chromatic contrast or large dewlap area) a species employs. More broadly, these results highlight that each component in a signal (such as colour or size) may be influenced by different selection pressures and that by assessing components in idually, we can gain a greater understanding of the evolution of signal ersity.
Phylogenetic evidence of historic mitochondrial introgression and cryptic diversity in the genus Pseudemoia (Squamata: Scincidae)
Publisher: Elsevier BV
Date: 12-2014
DOI: 10.1016/J.YMPEV.2014.09.006
Abstract: The Australian scincid genus Pseudemoia comprises six morphologically similar species restricted to temperate south-eastern Australia. Due to the high degree of morphological conservatism, phylogenetic relationships and taxonomic status within the Pseudemoia entrecasteauxii complex (comprising the nominal species P. entrecasteauxii, P. cryodroma, and P. pagenstecheri) remains unresolved. To further investigate the phylogenetic relationships and taxonomic status of Pseudemoia spp., and to test the hypothesis that P. cryodroma evolved from hybridization between P. entrecasteauxii and P. pagenstecheri, we sequenced one mitochondrial locus (ND4) and five nuclear loci (β-globin, LGMN, PRLR, Rhodopsin, RPS8). While we find strong support for the monophyly of the P. entrecasteauxii complex, there exists marked incongruence between the mitochondrial and nuclear markers, particularly in regards to the high altitude specialist, P. cryodroma. The most parsimonious explanation of this discordance is historic mitochondrial introgression, although a hybrid origin for P. cryodroma cannot be completely rejected. Within P. pagenstecheri sensu lato, we identified a strongly supported, highly ergent yet morphologically cryptic lineage restricted to northern New South Wales. Although more weakly supported by the nuDNA, we also identified a second geographically distinct lineage of P. pagenstecheri s.l., which may warrant separate conservation management. Our study reveals a more complex evolutionary history of the genus Pseudemoia than previously appreciated and contributes to our understanding of the biogeography and evolution of Australian mesic zone fauna.
Bio-informed materials: three guiding principles for innovation informed by biology
Publisher: Springer Science and Business Media LLC
Date: 08-08-2023
Stress‐induced changes in color expression mediated by iridophores in a polymorphic lizard
Publisher: Wiley
Date: 07-09-2017
DOI: 10.1002/ECE3.3349
The biology of color
Publisher: American Association for the Advancement of Science (AAAS)
Date: 04-08-2017
Abstract: Animals live in a colorful world, but we rarely stop to think about how this color is produced and perceived, or how it evolved. Cuthill et al. review how color is used for social signals between in idual animals and how it affects interactions with parasites, predators, and the physical environment. New approaches are elucidating aspects of animal coloration, from the requirements for complex cognition and perception mechanisms to the evolutionary dynamics surrounding its development and ersification. Science , this issue p. eaan0221
Convergence and divergence in lizard colour polymorphisms
Publisher: Wiley
Date: 08-10-2020
DOI: 10.1111/BRV.12656
Revealing the Biochemical and Genetic Basis of Color Variation in a Polymorphic Lizard
Publisher: Oxford University Press (OUP)
Date: 18-04-2017
Abstract: Determining the mechanistic and genetic basis of animal coloration is essential to understand the costs and constraints on color production, and the evolution and maintenance of phenotypic variation. However, genes underlying structural color and widespread pigment classes apart from melanin remain largely uncharacterized, in part due to restricted taxonomic focus. We combined liquid chromatography-mass spectrometry and RNA-seq gene expression analyses to characterize the pigments and genes associated with skin color in the polymorphic lizard, Ctenophorus decresii. Throat coloration in male C. decresii may be a combination of orange, yellow, grey, or ultra-violet blue. We confirmed the presence of two biochemically different pigment classes, pteridines (self-synthesized) and carotenoids (acquired through the diet), in all skin colors. Orange skin had the highest levels of pteridine pigments while yellow skin tended to have higher levels of carotenoids, of which the vitamin A precursors β-carotene and β-cryptoxanthin have not been previously confirmed in reptiles. These results were confirmed by gene expression analyses, which detected 489 genes differentially expressed between the skin colors, including genes associated with pteridine production, provitamin A carotenoid metabolism, iridophore-specific synthesis, melanin synthesis, and steroid hormone pathways. For the majority of these 489 genes, however, our study reveals a new association with color production in vertebrates. These data represent a significant contribution to understanding the genetic basis of color variation in vertebrates and a rich resource for further studies.
Do female Lake Eyre dragon lizards adjust courtship rejection behaviour under higher predation risk?
Publisher: Brill
Date: 2010
Phylogeographic structure, demographic history and morph composition in a colour polymorphic lizard
Publisher: Wiley
Date: 21-08-2014
DOI: 10.1111/JEB.12464
Abstract: In polymorphic species, population ergence in morph composition and frequency has the potential to promote speciation. We assessed the relationship between geographic variation in male throat colour polymorphism and phylogeographic structure in the tawny dragon lizard, Ctenophorus decresii. We identified four genetically distinct lineages, corresponding to two polymorphic lineages in the Northern Flinders Ranges and Southern Flinders Ranges/Olary Ranges regions respectively, and a monomorphic lineage in the Mt Lofty Ranges/Kangaroo Island region. The degree of ergence between these three lineages was consistent with isolation to multiple refugia during Pleistocene glacial cycles, whereas a fourth, deeply ergent (at the interspecific level) and monomorphic lineage was restricted to western New South Wales. The same four morphs occurred in both polymorphic lineages, although populations exhibited considerable variation in the frequency of morphs. By contrast, male throat coloration in the monomorphic lineages differed from each other and from the polymorphic lineages. Our results suggest that colour polymorphism has evolved once in the C. decresii species complex, with subsequent loss of polymorphism in the Mt Lofty Ranges/Kangaroo Island lineage. However, an equally parsimonious scenario, that polymorphism arose independently twice within C. decresii, could not be ruled out. We also detected evidence of a narrow contact zone with limited genotypic admixture between the polymorphic Olary Ranges and monomorphic Mt Lofty Ranges regions, yet no in iduals of intermediate colour phenotype. Such genetic ergence and evidence for barriers to gene flow between lineages suggest incipient speciation between populations that differ in morph composition.
Red carotenoids and associated gene expression explain colour variation in frillneck lizards
Publisher: The Royal Society
Date: 17-07-2019
Abstract: A long-standing hypothesis in evolutionary ecology is that red–orange ornamental colours reliably signal in idual quality owing to limited dietary availability of carotenoids and metabolic costs associated with their production, such as the bioconversion of dietary yellow carotenoids to red ketocarotenoids. However, in ectothermic vertebrates, these colours can also be produced by self-synthesized pteridine pigments. As a consequence, the relative ratio of pigment types and their biochemical and genetic basis have implications for the costs and information content of colour signals yet they remain poorly known in most taxonomic groups. We tested whether red- and yellow-frilled populations of the frillneck lizard, Chlamydosaurus kingii, differ in the ratio of different biochemical classes of carotenoid and pteridine pigments, and examined associated differences in gene expression. We found that, unlike other squamate reptiles, red hues derive from a higher proportion of ketocarotenoids relative to both dietary yellow carotenoids and to pteridines. Whereas red frill skin showed higher expression of several genes associated with carotenoid metabolism, yellow frill skin showed higher expression of genes associated with steroid hormones. Based on the different mechanisms underlying red and yellow signals, we hypothesize that frill colour conveys different information in the two populations. More generally, the data expand our knowledge of the genetic and biochemical basis of colour signals in vertebrates.
Conserved visual sensitivities across divergent lizard lineages that differ in an ultraviolet sexual signal
Publisher: Wiley
Date: 27-09-2019
DOI: 10.1002/ECE3.5686
Perception of contextual size illusions by honeybees in restricted and unrestricted viewing conditions
Publisher: The Royal Society
Date: 22-11-2017
Abstract: How different visual systems process images and make perceptual errors can inform us about cognitive and visual processes. One of the strongest geometric errors in perception is a misperception of size depending on the size of surrounding objects, known as the Ebbinghaus or Titchener illusion. The ability to perceive the Ebbinghaus illusion appears to vary dramatically among vertebrate species, and even populations, but this may depend on whether the viewing distance is restricted. We tested whether honeybees perceive contextual size illusions, and whether errors in perception of size differed under restricted and unrestricted viewing conditions. When the viewing distance was unrestricted, there was an effect of context on size perception and thus, similar to humans, honeybees perceived contrast size illusions. However, when the viewing distance was restricted, bees were able to judge absolute size accurately and did not succumb to visual illusions, despite differing contextual information. Our results show that accurate size perception depends on viewing conditions, and thus may explain the wide variation in previously reported findings across species. These results provide insight into the evolution of visual mechanisms across vertebrate and invertebrate taxa, and suggest convergent evolution of a visual processing solution.
Environment, but not genetic divergence, influences geographic variation in colour morph frequencies in a lizard
Publisher: Springer Science and Business Media LLC
Date: 08-08-2015
DOI: 10.1186/S12862-015-0442-X
Abstract: Identifying the causes of intraspecific phenotypic variation is essential for understanding evolutionary processes that maintain ersity and promote speciation. In polymorphic species, the relative frequencies of discrete morphs often vary geographically yet the drivers of spatial variation in morph frequencies are seldom known. Here, we test the relative importance of gene flow and natural selection to identify the causes of geographic variation in colour morph frequencies in the Australian tawny dragon lizard, Ctenophorus decresii . Populations of C. decresii are polymorphic for male throat coloration and all populations surveyed shared the same four morphs but differed in the relative frequencies of morphs. Despite genetic structure among populations, there was no relationship between genetic similarity or geographic proximity and similarity in morph frequencies. However, we detected remarkably strong associations between morph frequencies and two environmental variables (mean annual aridity index and vegetation cover), which together explained approximately 45 % of the total variance in morph frequencies. Spatial variation in selection appears to play an important role in shaping morph frequency patterns in C. decresii . Selection associated with differences in local environmental conditions, combined with relatively low levels of gene flow, is expected to favour population ergence in morph composition, but may be counteracted by negative frequency-dependent selection favouring rare morphs.
Ornament evolution in dragon lizards: multiple gains and widespread losses reveal a complex history of evolutionary change
Publisher: Wiley
Date: 08-12-2006
DOI: 10.1111/J.1420-9101.2005.01050.X
Abstract: The expression in females of ornaments thought to be the target of sexual selection in males is a long-standing puzzle. Two main hypotheses are proposed to account for the existence of conspicuous ornaments in both sexes (mutual ornamentation): genetic correlation between the sexes and sexual selection on females as well as males. We examined the pattern of ornament gains and losses in 240 species of dragon lizards (Agamidae) in order to elucidate the relative contribution of these two factors in the evolution of mutual ornamentation. In addition, we tested whether the type of shelter used by lizards to avoid predators predicts the evolutionary loss or constraint of ornament expression. We found evidence that the origin of female ornaments is broadly consistent with the predictions of the genetic correlation hypothesis. Ornaments appear congruently in both sexes with some lineages subsequently evolving male biased sexual dimorphism, apparently through the process of natural selection for reduced ornamentation in females. Nevertheless, ornaments have also frequently evolved in both sexes independently. This suggests that genetic correlations are potentially weak for several lineages and sexual selection on females is responsible for at least some evolutionary change in this group. Unexpectedly, we found that the evolutionary loss of some ornaments is concentrated more in males than females and this trend cannot be fully explained by our measures of natural selection.
Specific MHC class I supertype associated with parasite infection and color morph in a wild lizard population
Publisher: Wiley
Date: 17-09-2018
DOI: 10.1002/ECE3.4479
Reflection of near-infrared light confers thermal protection in birds
Publisher: Springer Science and Business Media LLC
Date: 06-09-2018
DOI: 10.1038/S41467-018-05898-8
Abstract: Biologists have focused their attention on the optical functions of light reflected at ultraviolet and human-visible wavelengths. However, most radiant energy in sunlight occurs in ‘unseen’ near-infrared (NIR) wavelengths. The capacity to reflect solar radiation at NIR wavelengths may enable animals to control heat gain and remain within their critical thermal limits. Here, using a continent-wide phylogenetic analysis of Australian birds, we show that species occupying hot, arid environments reflect more radiant energy in NIR wavelengths than species in thermally benign environments, even when controlling for variation in visible colour. Biophysical models confirm that smaller species gain a greater advantage from high NIR reflectivity in hot, arid environments, reducing water loss from compensatory evaporative cooling by up to 2% body mass per hour. These results highlight the importance of NIR reflectivity for thermal protection, which may become increasingly critical as the frequency of extreme climatic events increases.
Sexual selection, natural selection and the evolution of dimorphic coloration and ornamentation in agamid lizards
Publisher: The Royal Society
Date: 07-11-2004
Can scent-mediated female mate preference explain an abrupt mtDNA cline in Lacerta schreiberi?
Publisher: Brill
Date: 2009
Abstract: Divergence in female mate preferences can strongly influence the structure and dynamics of hybrid zones. We examined the potential role of female mate preferences in maintaining an abrupt west-east mtDNA cline between two deeply ergent genetic lineages of Lacerta schreiberi, a lizard endemic to the Iberian Peninsula. The lineages are largely morphologically cryptic but with respect to the mtDNA cline, western males tend to be less parasitized, in better body condition and more intensely coloured than eastern males, a pattern that cannot be explained by environmental variation alone. The lineages may also differ in unmeasured aspects such as physiology, behaviour and olfactory signals, which may influence mate choice. As female mate attraction has been found to vary with olfactory cues in lacertid lizards, we experimentally tested whether females were differentially attracted to femoral pore secretions of males from the two genetic backgrounds. Females did not prefer scents of 'higher quality' western males, nor did they prefer the scents of males belonging to their own genetic background. This suggests the abrupt mtDNA cline is unlikely to be explained by assortative mating of matrilineages that distinguish male genetic background based on scent.
The Paradox of Iridescent Signals
Publisher: Elsevier BV
Date: 03-2021
Spectral sensitivity of cone photoreceptors and opsin expression in two colour-divergent lineages of the lizard Ctenophorus decresii
Publisher: The Company of Biologists
Date: 09-2015
DOI: 10.1242/JEB.131854
The eyes have it: dim-light activity is associated with the morphology of eyes but not antennae across insect orders
Publisher: Oxford University Press (OUP)
Date: 12-07-2021
DOI: 10.1093/BIOLINNEAN/BLAB088
Abstract: The perception of cues and signals in visual, olfactory and auditory modalities underpins all animal interactions and provides crucial fitness-related information. Sensory organ morphology is under strong selection to optimize detection of salient cues and signals in a given signalling environment, the most well-studied ex le being selection on eye design in different photic environments. Many dim-light active species have larger compound eyes relative to body size, but little is known about differences in non-visual sensory organ morphology between diurnal and dim-light active insects. Here, we compare the micromorphology of the compound eyes (visual receptors) and antennae (olfactory and mechanical receptors) in representative pairs of day active and dim-light active species spanning multiple taxonomic orders of insects. We find that dim-light activity is associated with larger compound eye ommatidia and larger overall eye surface area across taxonomic orders but find no evidence that morphological adaptations that enhance the sensitivity of the eye in dim-light active insects are accompanied by morphological traits of the antennae that may increase sensitivity to olfactory, chemical or physical stimuli. This suggests that the ecology and natural history of species is a stronger driver of sensory organ morphology than is selection for complementary investment between sensory modalities.
The genetic basis of discrete and quantitative colour variation in the polymorphic lizard, Ctenophorus decresii
Publisher: Springer Science and Business Media LLC
Date: 06-09-2016
Multiscale Evaluation of Thermal Dependence in the Glucocorticoid Response of Vertebrates
Publisher: University of Chicago Press
Date: 02-09-2016
DOI: 10.1086/687588
Abstract: Environmental temperature has profound effects on animal physiology, ecology, and evolution. Glucocorticoid (GC) hormones, through effects on phenotypic performance and life history, provide fundamental vertebrate physiological adaptations to environmental variation, yet we lack a comprehensive understanding of how temperature influences GC regulation in vertebrates. Using field studies and meta- and comparative phylogenetic analyses, we investigated how acute change and broadscale variation in temperature correlated with baseline and stress-induced GC levels. Glucocorticoid levels were found to be temperature and taxon dependent, but generally, vertebrates exhibited strong positive correlations with acute changes in temperature. Furthermore, reptile baseline, bird baseline, and capture stress-induced GC levels to some extent covaried with broadscale environmental temperature. Thus, vertebrate GC function appears clearly thermally influenced. However, we caution that lack of detailed knowledge of thermal plasticity, heritability, and the basis for strong phylogenetic signal in GC responses limits our current understanding of the role of GC hormones in species' responses to current and future climate variation.
Elevation of Divergent Color Polymorphic and Monomorphic Lizard Lineages (Squamata: Agamidae) to Species Level
Publisher: American Society of Ichthyologists and Herpetologists (ASIH)
Date: 25-03-2021
DOI: 10.1643/H2020064
Multiple paternity but no evidence of biased sperm use in female dumpling squid Euprymna tasmanica
Publisher: Inter-Research Science Center
Date: 24-09-2014
DOI: 10.3354/MEPS10898
Marked colour divergence in the gliding membranes of a tropical lizard mirrors population differences in the colour of falling leaves
Publisher: The Royal Society
Date: 12-2014
Abstract: Populations of the Bornean gliding lizard, Draco cornutus , differ markedly in the colour of their gliding membranes. They also differ in local vegetation type (mangrove forest versus lowland rainforest) and consequently, the colour of falling leaves (red and brown/black in mangrove versus green, brown and black in rainforest). We show that the gliding membranes of these lizards closely match the colours of freshly fallen leaves in the local habitat as they appear to the visual system of birds (their probable predators). Furthermore, gliding membranes more closely resembled colours of local fallen leaves than standing foliage or fallen leaves in the other population's habitat. This suggests that the two populations have erged in gliding membrane coloration to match the colours of their local falling leaves, and that mimicking falling leaves is an adaptation that functions to reduce predation by birds.
Space use and genetic structure do not maintain color polymorphism in a species with alternative behavioral strategies
Publisher: Wiley
Date: 26-12-2018
DOI: 10.1002/ECE3.4729
Geographic variation in animal colour polymorphisms and its role in speciation
Publisher: Wiley
Date: 14-02-2014
DOI: 10.1111/BRV.12083
Abstract: Polymorphic species, in which multiple variants coexist within a population, are often used as model systems in evolutionary biology. Recent research has been dominated by the hypothesis that polymorphism can be a precursor to speciation. To date, the majority of research regarding polymorphism and speciation has focused on whether polymorphism is maintained within a population or whether morphs within populations may erge to form separate species (sympatric speciation) however, the geographical context of speciation in polymorphic systems is likely to be both erse and complex. In this review, we draw attention to the geographic variation in morph composition and frequencies that characterises many, if not most polymorphic species. Recent theoretical and empirical developments suggest that such variation in the number, type and frequency of morphs present among populations can increase the probability of speciation. Thus, the geographical context of a polymorphism requires a greater research focus. Here, we review the prevalence, causes and evolutionary consequences of geographic variation in polymorphism in colour-polymorphic animal species. The prevalence and nature of geographic variation in polymorphism suggests that polymorphism may be a precursor to and facilitate speciation more commonly than appreciated previously. We argue that a better understanding of the processes generating geographic variation in polymorphism is vital to understanding how polymorphism can promote speciation.
Male‐biased sexual selection, but not sexual dichromatism, predicts speciation in birds
Publisher: Wiley
Date: 07-03-2021
DOI: 10.1111/EVO.14183
Genetics and evolution of colour patterns in reptiles
Publisher: Elsevier BV
Date: 06-2013
DOI: 10.1016/J.SEMCDB.2013.04.001
Abstract: The study of coloration in the polyphyletic reptilians has flourished in the last two decades, in particular with respect to the underlying genetics of colour traits, the function of colours in social interactions, and ongoing selection on these traits in the wild. The taxonomic bias, however, is profound: at this level of resolution almost all available information is for diurnal lizards. Therefore, we focus on case studies, for which there are as complete causal sequences of colour evolution as possible, from phenotypic expression of variation in colour, to ongoing selection in the wild. For work prior to 1992 and for a broader coverage of reptilian coloration we refer the readers to Cooper and Greenburg's (Biology of the Reptilia, 1992) review. There are seven major conclusions we would like to emphasise: (a) visual systems in diurnal lizards are broadly conserved but among the wider range of reptiles in general, there is functionally important variation in the number and type of photoreceptors, spectral tuning of photopigments and optical properties of the eye (b) coloration in reptiles is a function of complex interactions between structural and pigmentary components, with implications for both proximate control and condition dependence of colour expression (c) studies of colour-variable species have enabled estimates of heritability of colour and colour patterns, which often show a simple Mendelian pattern of inheritance (d) colour-polymorphic lizard species sometimes, but not always, show striking differences in genetically encoded reproductive tactics and provide useful models for studying the evolution and maintenance of polymorphism (e) both male and female colours are sometimes, but not always, a significant component of socio-sexual signalling, often based on multiple traits (f) evidence for effects of hormones and condition on colour expression, and trade-offs with immunocompetence and parasite load, is variable (g) lizards show fading of colours in response to physiological stress and ageing and are hence likely to be appropriate models for work on the interactions between handicaps, indicator traits, parasitology and immunoecology.
Spectral sensitivity of cone photoreceptors and opsin expression in two colour-divergent lineages of the lizardCtenophorus decresii
Publisher: The Company of Biologists
Date: 2015
DOI: 10.1242/JEB.119404
Abstract: Intraspecific differences in sensory perception are rarely reported but may occur when a species range extends across varying sensory environments, or there is coevolution between the sensory system and a varying signal. Ex les in colour vision and colour signals are rare in terrestrial systems. The tawny dragon lizard Ctenophorus decresii is a promising candidate for such intraspecific variation, because the species comprises two geographically and genetically distinct lineages in which throat colour (a social signal used in intra- and inter-specific interactions) is locally adapted to the habitat and differs between lineages. Male lizards from the southern lineage have UV-blue throats, whereas males from the northern lineage are polymorphic with four discrete throat colours that all show minimal UV reflectance. Here we determine the cone photoreceptor spectral sensitivities and opsin expression of the two lineages, to test whether they differ, particularly in the UV wavelengths. Using microspectrophotometry on retinal cone photoreceptors, we identified a long wavelength sensitive visual pigment, a ‘short’ and ‘long’ medium wavelength sensitive pigment and a short wavelength sensitive pigment, all of which did not differ in λmax between lineages. Through transcriptome analysis of opsin genes we found that both lineages express four cone opsin genes, including that SWS1 opsin with peak sensitivity in the UV range, and that amino acid sequences did not differ between lineages with the exception of a single leucine/valine substitution in the RH2 opsin. Counts of yellow and transparent oil droplets associated with LWS+MWS and SWS+UVS cones respectively showed no difference in relative cone proportions between lineages. Therefore, contrary to predictions, we find no evidence of differences between lineages in single cone photoreceptor spectral sensitivity or opsin expression however, we confirm the presence of four single cones classes and thus likely tetrachromacy in C. decresii, and provide the first evidence of UV sensitivity in agamid lizards.
Sexual Selection And The Evolution Of Complex Color Patterns In Dragon Lizards
Publisher: Wiley
Date: 11-06-2012
DOI: 10.1111/J.1558-5646.2012.01698.X
Abstract: Many species have elaborate and complex coloration and patterning, which often differ between the sexes. Sexual selection may increase the size or intensity of color patches (elaboration) in one sex or drive the evolution of novel signal elements (innovation). The latter potentially increases color pattern complexity. Color pattern complexity may also be influenced by ecological factors related to predation and environment however, very few studies have investigated the effects of both sexual and natural selection on color pattern complexity across species. We used a phylogenetic comparative approach to examine these effects in 85 species and subspecies of Australian dragon lizards (family Agamidae). We quantified color pattern complexity by adapting the Shannon-Wiener ersity index. There were clear sex differences in color pattern complexity, which were positively correlated with both sexual dichromatism and sexual size dimorphism, consistent with the idea that sexual selection plays a significant role in the evolution of color pattern complexity. By contrast, we found little evidence of a link between environmental factors and color pattern complexity on body regions exposed to predators. Our results suggest that sexual selection rather than natural selection has led to increased color pattern complexity in males.
The gender gap in science: How long until women are equally represented?
Publisher: Public Library of Science (PLoS)
Date: 19-04-2018
Factors shaping the evolution of colour patterns in Australian agamid lizards (Agamidae): A comparative study
Publisher: Oxford University Press (OUP)
Date: 15-03-2013
DOI: 10.1111/BIJ.12030
Last male sperm precedence in a polygamous squid
Publisher: Oxford University Press (OUP)
Date: 12-06-2015
DOI: 10.1111/BIJ.12590
Multiple signals in chameleon contests: designing and analysing animal contests as a tournament
Publisher: Elsevier BV
Date: 06-2006
Camouflage and colour change: antipredator responses to bird and snake predators across multiple populations in a dwarf chameleon
Publisher: Oxford University Press (OUP)
Date: 15-06-2006
Geographic variation in hybridization and ecological differentiation between three syntopic, morphologically similar species of montane lizards
Publisher: Wiley
Date: 18-05-2016
DOI: 10.1111/MEC.13652
Abstract: To understand factors shaping species boundaries in closely related taxa, a powerful approach is to compare levels of genetic admixture at multiple points of contact and determine how this relates to intrinsic and extrinsic factors, such as genetic, morphological and ecological differentiation. In the Australian Alps, the threatened alpine bog skink Pseudemoia cryodroma co-occurs with two morphologically and ecologically similar congeners, P. entrecasteauxii and P. pagenstecheri, and all three species are suspected to hybridize. We predicted that the frequency of hybridization should be negatively correlated with genetic ergence, morphological differentiation and microhabitat separation. We tested this hypothesis using a mitochondrial locus, 13 microsatellite loci, morphological and microhabitat data and compared results across three geographically isolated sites. Despite strong genetic structure between species, we detected hybridization between all species pairs, including evidence of backcrossed in iduals at the two sites where all three species are syntopic. Hybridization frequencies were not consistently associated with genetic, morphological or ecological differentiation. Furthermore, P. entrecasteauxii and P. pagenstecheri only hybridized at the two sites where they are syntopic with P. cryodroma, but not at the largest site where P. cryodroma was not recorded, suggesting that P. cryodroma may serve as a bridging species. This study reveals the complex dynamics within a three species hybrid zone and provides a baseline for assessing the impact of climate change and anthropogenic habitat modification on future hybridization frequencies.
Natural Selection on Social Signals: Signal Efficacy and the Evolution of Chameleon Display Coloration
Publisher: University of Chicago Press
Date: 12-2007
DOI: 10.1086/522835
Abstract: Whether general patterns of signal evolution can be explained by selection for signal efficacy (detectability) has yet to be established. To establish the importance of signal efficacy requires evidence that both signals and their detectability to receivers have evolved in response to habitat shifts in a predictable fashion. Here, we test whether habitat structure has predictable effects on the evolution of male and female display coloration in 21 lineages of African dwarf chameleon (Bradypodion), based on a phylogenetic comparative analysis. We used quantitative measures of display coloration and estimated signal detectability as the contrast of those colors among body regions or against the background vegetation as perceived by the chameleon visual system. Both male and female display colors varied predictably with different aspects of habitat structure. In several (but not all) instances, habitat-associated shifts in display coloration resulted in habitat-associated variation in detectability. While males exhibit a remarkable variety of colors and patterns, female display coloration is highly conserved, consisting in all populations of contrasting dark and light elements. This color pattern may maximize detectability across all habitat types, potentially explaining female conservatism. Overall, our results support the view that selection for signal efficacy plays an important role in the evolution of animal signals.
Predator-specific camouflage in chameleons
Publisher: The Royal Society
Date: 20-05-2008
Abstract: A crucial problem for most animals is how to deal with multiple types of predator, which differ in their sensory capabilities and methods of prey detection. For animals capable of rapid colour change, one potential strategy is to change their appearance in relation to the threat posed by different predators. Here, we show that the dwarf chameleon, Bradypodion taeniabronchum , exhibits different colour responses to two predators that differ in their visual capabilities. Using a model of animal colour perception to gain a ‘predator's eye view’, we show that chameleons showed better background colour matching in response to birds than snakes, yet they appear significantly more camouflaged to the snake visual system because snakes have poorer colour discrimination.
A generalized approach to characterize optical properties of natural objects
Publisher: Oxford University Press (OUP)
Date: 25-09-2022
DOI: 10.1093/BIOLINNEAN/BLAC064
Abstract: To understand the ersity of ways in which natural materials interact with light, it is important to consider how their reflectance changes with the angle of illumination or viewing and to consider wavelengths beyond the visible. Efforts to characterize these optical properties, however, have been h ered by heterogeneity in measurement techniques, parameters and terminology. Here, we propose a standardized set of measurements, parameters and terminology to describe the optical properties of natural objects based on spectrometry, including angle-dependent effects, such as iridescence and specularity. We select a set of existing measurements and parameters that are generalizable to any wavelength range and spectral shape, and we highlight which subsets of measures are relevant to different biological questions. As a case study, we have applied these measures to 30 species of Christmas beetles, in which we observed previously unrealized ersity in visible and near-infrared reflectance. As expected, reflection of short wavelengths was associated with high spectral purity and angle dependence. In contrast to simple, artificial structures, iridescence and specularity were not strongly correlated, highlighting the complexity and modularity of natural materials. Species did not cluster according to spectral parameters or genus, suggesting high lability of optical properties. The proposed standardization of measures and parameters will improve our understanding of biological adaptations for manipulating light by facilitating the systematic comparison of complex optical properties, such as glossy or metallic appearances and visible or near-infrared iridescence.
Disentangling thermal from alternative drivers of reflectance in jewel beetles: A macroecological study
Publisher: Wiley
Date: 11-01-2023
DOI: 10.1111/GEB.13632
Abstract: To predict future colour–climate relationships, it is important to distinguish thermal drivers of reflectance from other evolutionary drivers. We aimed to achieve this by comparing relationships between climate and coloration in ultraviolet–visible (UV–Vis) and near‐infrared (NIR) light, separately. S les were distributed primarily across Australia and North America, with some from Africa and Asia. Coleoptera: Buprestidae. We used jewel beetles as models to identify climatic drivers of reflectance, because jewel beetles have highly erse coloration and a wide distribution and are often active in hot conditions. Specifically, we tested the association between climate, body size and reflectance using a phylogenetic comparative analysis for three wavebands (UV–Vis, NIR and total). Reflectance of jewel beetles was more strongly predicted by body size than by climate. NIR reflectance and total reflectance were not associated with climate, but larger beetles had higher NIR reflectance. For UV–Vis reflectance, small beetles were darker in warmer and more humid environments, whereas there was no association with climate for large beetles. Our study suggests that variation in reflectance of jewel beetles is not driven by thermal requirements and highlights the importance of considering NIR reflectance when evaluating explanations of the effects of colour on thermoregulation.
Geographic divergence and colour change in response to visual backgrounds and illumination intensity in bearded dragons
Publisher: The Company of Biologists
Date: 15-03-2017
DOI: 10.1242/JEB.148544
Abstract: Animals may improve camouflage by both dynamic colour change and local evolutionary adaptation of colour but we have little understanding of their relative importance in colour-changing species. We tested for differences in colour change in response to background colour and light intensity in two populations of central bearded dragon lizards (Pogona vitticeps) representing the extremes in body coloration and geographical range. We found that bearded dragons change colour in response to various backgrounds and that colour change is affected by illumination intensity. Within-in idual colour change was similar in magnitude in the two populations but varied between backgrounds. However, at the endpoints of colour change, each population showed greater similarity to backgrounds that were representative of the local habitat compared with the other population, indicating local adaptation to visual backgrounds. Our results suggest that even in species that change colour, both phenotypic plasticity and geographic ergence of coloration may contribute to improved camouflage.
Color Change for Thermoregulation versus Camouflage in Free-Ranging Lizards
Publisher: University of Chicago Press
Date: 12-2016
DOI: 10.1086/688765
Abstract: Animal coloration has multiple functions including thermoregulation, camouflage, and social signaling, and the requirements of each function may sometimes conflict. Many terrestrial ectotherms accommodate the multiple functions of color through color change. However, the relative importance of these functions and how color-changing species accommodate them when they do conflict are poorly understood because we lack data on color change in the wild. Here, we show that the color of in idual radio-tracked bearded dragon lizards, Pogona vitticeps, correlates strongly with background color and less strongly, but significantly, with temperature. We found no evidence that in iduals simultaneously optimize camouflage and thermoregulation by choosing light backgrounds when hot or dark backgrounds when cold. In laboratory experiments, lizards showed both UV-visible (300-700 nm) and near-infrared (700-2,100 nm) reflectance changes in response to different background and temperature treatments, consistent with camouflage and thermoregulatory functions, respectively, but with no interaction between the two. Overall, our results suggest that wild bearded dragons change color to improve both thermoregulation and camouflage but predominantly adjust for camouflage, suggesting that compromising camouflage may entail a greater potential immediate survival cost.
Colour change on different body regions provides thermal and signalling advantages in bearded dragon lizards
Publisher: The Royal Society
Date: 15-06-2016
Abstract: Many terrestrial ectotherms are capable of rapid colour change, yet it is unclear how these animals accommodate the multiple functions of colour, particularly camouflage, communication and thermoregulation, especially when functions require very different colours. Thermal benefits of colour change depend on an animal's absorptance of solar energy in both UV–visible (300–700 nm) and near-infrared (NIR 700–2600 nm) wavelengths, yet colour research has focused almost exclusively on the former. Here, we show that wild-caught bearded dragon lizards ( Pogona vitticeps ) exhibit substantial UV–visible and NIR skin reflectance change in response to temperature for dorsal but not ventral (throat and upper chest) body regions. By contrast, lizards showed the greatest temperature-independent colour change on the beard and upper chest during social interactions and as a result of circadian colour change. Biophysical simulations of heat transfer predicted that the maximum temperature-dependent change in dorsal reflectivity could reduce the time taken to reach active body temperature by an average of 22 min per active day, saving 85 h of basking time throughout the activity season. Our results confirm that colour change may serve a thermoregulatory function, and competing thermoregulation and signalling requirements may be met by partitioning colour change to different body regions in different circumstances.
Very low rate of multiple paternity detected in clutches of a wild agamid lizard
Publisher: CSIRO Publishing
Date: 2017
DOI: 10.1071/ZO18006
Abstract: Genetic mating systems described for squamate reptiles range from primarily monogamous to completely polygynandrous. The presence of female multiple mating is almost ubiquitous among squamates and even occurs, albeit at a low rate, in socially monogamous species. Here we examine the genetic mating system of the territorial tawny dragon lizard (Ctenophorus decresii). Paternity was assigned to captive-born hatchlings using eight microsatellite loci, revealing a 4% rate of multiple paternity. One-quarter of males sired more than one clutch, although multiple mating by males is likely underestimated. The rate of multiple paternity in C. decresii represents one of the lowest among squamates and may be a result of successful male territoriality. However, the observed low rate of multiple paternity does not eliminate the possibility of widespread female multiple mating due to the potential for sperm storage and sperm competition. We conclude that the tawny dragon lizard employs a predominantly polygynous genetic mating system.
Rival assessment and comparison of morphological and performance-based predictors of fighting ability in Lake Eyre dragon lizards, Ctenophorus maculosus
Publisher: Springer Science and Business Media LLC
Date: 31-12-2014
Microplastics in intertidal water of South Australia and the mussel Mytilus spp.; the contrasting effect of population on concentration
Publisher: Elsevier BV
Date: 07-2022
DOI: 10.1016/J.SCITOTENV.2022.154875
Abstract: Microplastics, plastic particles <5 mm in size, are of global concern as human-caused pollutants in marine and fresh waters, and yet little is known of their distribution, behaviour and ecological impact in the intertidal environment of South Australia. This study confirms for the first time, the presence of microplastic in the South Australian intertidal ecosystem by quantifying the abundance of particles in intertidal water and in the keystone species, the blue mussel, Mytilus spp., an important fisheries species, at ten and six locations respectively, along the South Australian coastline. For a remote region known for its pristine environment, microplastic concentration in intertidal water was found to be low to moderate (mean = 8.21 particles l
Maternal reproductive output and F1 hybrid fitness may influence contact zone dynamics
Publisher: Wiley
Date: 26-02-2021
DOI: 10.1111/JEB.13772
Abstract: The outcome of secondary contact between ergent lineages or species may be influenced by both the reproductive traits of parental species and the fitness of offspring however, their relative contributions have rarely been evaluated, particularly in longer‐lived vertebrate species. We performed pure and reciprocal laboratory crosses between Ctenophorus decresii (tawny dragon) and C. modestus (swift dragon) to examine how parental reproductive traits and ecologically relevant offspring fitness traits may explain contact zone dynamics in the wild. The two species meet in a contact zone of post‐F1 hybrids with asymmetric backcrossing and predominantly C. modestus mtDNA haplotypes. We found no evidence for reduced parental fecundity or offspring fitness for F1 hybrid crosses. However, maternal reproductive strategy differed between species, irrespective of the species of their mate. Ctenophorus modestus females had higher fecundity and produced more and larger clutches with lower embryonic mortality. Parental species also influenced sex ratios and offspring traits, with C. modestus ♀ × C. decresii ♂ hybrids exhibiting higher trait values for more fitness measures (growth rate, sprint speed, bite force) than offspring from all other pairings. Together, these patterns are consistent with the prevalence of C. modestus mtDNA in the contact zone, and asymmetric backcrossing likely reflects fitness effects that manifest in the F2 generation. Our results highlight how parental species can influence multiple offspring traits in different ways, which together may combine to influence offspring fitness and shape contact zone dynamics.
Male dwarf chameleons assess risk of courting large, aggressive females
Publisher: The Royal Society
Date: 20-05-2005
Abstract: Conflict between the sexes has traditionally been studied in terms of costs of mating to females and female resistance. However, courting can also be costly to males, especially when females are larger and aggressively resist copulation attempts. We examined male display intensity towards females in the Cape dwarf chameleon, Bradypodion pumilum , in which females are larger than males and very aggressive. We assessed whether aggressive female rejection imposes potential costs on males and whether males vary their display behaviour with intensity of female rejection, female size or relative size differences. Males persisted in courtship after initial female rejection in 84% of trials, and were bitten in 28% of trials. Attempted mounts were positively associated with males being bitten. Males reduced courtship with increased intensity of female rejection. Male courtship behaviour also varied with female size: males were more likely to court and approach smaller females, consistent with the hypothesis that larger females can inflict more damage. These results suggest that, in addition to assessing female willingness to mate, male dwarf chameleons may use courtship displays to assess potential costs of persistence, including costs associated with aggressive female rejection, weighed against potential reproductive pay-offs associated with forced copulation.
Local adaptation and divergence in colour signal conspicuousness between monomorphic and polymorphic lineages in a lizard
Publisher: Wiley
Date: 20-10-2014
DOI: 10.1111/JEB.12521
Abstract: Population differences in visual environment can lead to ergence in multiple components of animal coloration including signalling traits and colour patterns important for camouflage. Divergence may reflect selection imposed by different receivers (conspecifics, predators), which depends in turn on the location of the colour patch. We tested for local adaptation of two genetically and phenotypically ergent lineages of a rock-inhabiting lizard, Ctenophorus decresii, by comparing the visual contrast of colour patches to different receivers in native and non-native environments. The lineages differ most notably in male throat coloration, which is polymorphic in the northern lineage and monomorphic in the southern lineage, but also differ in dorsal and lateral coloration, which is visible to both conspecifics and potential predators. Using models of animal colour vision, we assessed whether lineage-specific throat, dorsal and lateral coloration enhanced conspicuousness to conspecifics, increased crypsis to birds or both, respectively, when viewed against the predominant backgrounds from each lineage. Throat colours were no more conspicuous against native than non-native rock but contrasted more strongly with native lichen, which occurs patchily on rocks inhabited by C. decresii. Conversely, neck coloration (lateral) more closely matched native lichen. Furthermore, although dorsal coloration of southern males was consistently more conspicuous to birds than that of northern males, both lineages had similar absolute conspicuousness against their native backgrounds. Combined, our results are consistent with local adaptation of multiple colour traits in relation to multiple receivers, suggesting that geographic variation in background colour has influenced the evolution of lineage-specific coloration in C. decresii.
Gliding lizards use the position of the sun to enhance social display
Publisher: The Royal Society
Date: 02-2017
Abstract: Effective communication requires animal signals to be readily detected by receivers in the environments in which they are typically given. Certain light conditions enhance the visibility of colour signals and these conditions can vary depending on the orientation of the sun and the position of the signaller. We tested whether Draco sumatranus gliding lizards modified their position relative to the sun to enhance the conspicuousness of their throat-fan (dewlap) during social display to conspecifics. The dewlap was translucent, and we found that lizards were significantly more likely to orient themselves perpendicular to the sun when displaying. This increases the dewlap's radiance, and likely, its conspicuousness, by increasing the amount of light transmitted through the ornament. This is a rare ex le of a behavioural adaptation for enhancing the visibility of an ornament to distant receivers.
Social interactions generate mutually reinforcing selection for male aggression in Lake Eyre dragons
Publisher: Oxford University Press (OUP)
Date: 2016
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