The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform
Leo J Fleishman - One of the best experts on this subject based on the ideXlab platform.
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visual playback of colorful signals in the field supports sensory drive for signal detectability
Current Zoology, 2018Co-Authors: Alex R Gunderson, Leo J Fleishman, Manuel LealAbstract:Colorful visual signals are important systems for investigating the effects of signaling environments and receiver physiology on signal evolution as predicted by the sensory drive hypothesis. Support for the sensory drive hypothesis on color signal evolution is mostly based on documenting correlations between the properties of signals and habitat conditions under which the signals are given (i.e., a correlational approach) and less commonly on the use of mathematical models that integrate representations of visual environments, signal properties, and sensory systems (i.e., a functional approach). Here, we used an experimental approach in the field to evaluate signal efficacy of colorful lizard throat fans called Dewlaps that show geographic variation in the lizard Anolis cristatellus. We used a remote controlled apparatus to display "fake Dewlaps" to wild lizards to test for adaptive divergence in Dewlap brightness (i.e., perceived intensity) among populations in situ. We found evidence of local adaptation in Dewlap brightness consistent with the sensory drive hypothesis. Specifically, Dewlaps that had the brightness characteristics of local lizards were more likely to be detected than those with the brightness characteristics of non-local lizards. Our findings indicate that simplified mathematical representations of visual environments may allow robust estimates of relative detectability or conspicuousness in natural habitats. We have shown the feasibility of evaluating color signal efficacy experimentally under natural conditions and demonstrate the potential advantages of presenting isolated components of signals to an intended receiver to measure their contribution to signal function.
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Why do Anolis Dewlaps glow? An analysis of a translucent visual signal
Functional Ecology, 2015Co-Authors: Leo J Fleishman, Brianna Ogas, David M. Steinberg, Manuel LealAbstract:Summary Male anoline lizards utilize a colourful, expandable throat fan, called the Dewlap, to rapidly and unambiguously signal their presence and species identity to conspecifics. Under some viewing conditions, the Dewlaps of some species appear to glow vividly, because they transmit a great deal of diffuse light, creating a translucent signal. Translucent signals are probably found in many animal groups, but they have rarely been studied. We hypothesized that Dewlap translucence might (i) increase Dewlap/background luminance contrast or (ii) increase the reliability of the colour as a species recognition signal by lowering the colour discrimination threshold in low light conditions such as forest shade. We calculated Dewlap colour (spectral radiance) for the Jamaican lizard Anolis lineatopus at natural perch sites with, and without, the inclusion of transmitted light. Transmitted light did not significantly increase the magnitude of luminance contrast between the Dewlap and background. We plotted colours of Dewlaps, background patches of habitat and Dewlaps of sympatric species in an anoline perceptual colour space (the colour tetrahedron), based on the four classes of cone photoreceptors found in the retina. Using a newly developed approach, we used ellipsoidal plots of uncertainty to quantify perceptual overlap between Dewlap spectral radiance and values for natural distractor colours. Diffuse transmission of light through the Dewlap greatly reduced the perceptual overlap between the Dewlap and natural background colours. This finding strongly suggests that selection has favoured the evolution of a translucent Dewlap as a mechanism to increase the reliability of detection of the signal under the low light conditions. In general, any animal's colour signal must emit sufficient light intensity to allow the colour to be discriminated from other distractor colours in the habitat. This will tend to favour the evolution of colours with higher total intensity (i.e. higher reflectance and/or transmittance) in animals that signal in relatively low light conditions such as forest shade.
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Habitat light and Dewlap color diversity in four species of Puerto Rican anoline lizards
Journal of Comparative Physiology A, 2009Co-Authors: Leo J Fleishman, Manuel Leal, Matthew H. PersonsAbstract:Closely related species often have signals that differ dramatically in design. The evolution of such differences may be important in the process of speciation. Selection for signal detectability under different habitat conditions has been proposed as a mechanism leading to the evolution of signal diversity. We examined Dewlap color in four closely related species of Anolis lizards that occupy habitats with different light conditions. Initially, we tested the hypothesis that lizards choose specific light conditions within each habitat in which to signal. We rejected this hypothesis for all four species. We next calculated the detectability of the Dewlap color of all four species at display locations in each habitat. If selection for detectability under the different light conditions explained the divergence in signal design, the occupant of a given habitat was predicted to have the highest signal detectability in that habitat. However, the rank order of detectability of the four Dewlap colors was nearly the same in all four habitats. We concluded that divergent selection for signal detectability does not, by itself, explain the evolution of Dewlap color diversity. We hypothesize that the evolution of Dewlap color diversity results from simultaneous selection for multiple functions of Dewlap color.
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differences in visual signal design and detectability between allopatric populations of anolis lizards
The American Naturalist, 2004Co-Authors: Manuel Leal, Leo J FleishmanAbstract:Abstract: We tested the prediction of the sensory drive hypothesis using four allopatric populations of the lizard Anolis cristatellus from two distinct environments (i.e., mesic and xeric conditions). For each population, we measured habitat light characteristics and quantified signal design by measuring the spectral and total reflectance and transmittance of the Dewlap. We used these data to calculate Dewlap detectability using an empirically based model of signal detection probability. We found that populations from mesic and xeric conditions occupy two distinct habitats with respect to light intensity and spectral quality and that Dewlap design has diverged between populations in a way that increases signal detectability in each habitat. The major difference in Dewlap design was in total reflectance and transmittance, making Dewlaps from xeric habitats darker and Dewlaps from mesic habitats brighter. Furthermore, Dewlap detection decreased significantly when a Dewlap from a xeric habitat is detected u...
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evidence for habitat partitioning based on adaptation to environmental light in a pair of sympatric lizard species
Proceedings of The Royal Society B: Biological Sciences, 2002Co-Authors: Manuel Leal, Leo J FleishmanAbstract:Terrestrial habitats exhibit a variety of light environments. If species exhibit evolutionary adaptations of their visual system or signals to habitat light conditions, then these conditions can directly influence the structure of communities. We evaluated habitat light characteristics and visual-signal design in a pair of sympatric species of lizards: Anolis cooki and Anolis cristatellus. We found that each species occupies a distinct microhabitat with respect to light intensity and spectral quality. We measured the relative retinal spectral sensitivity and found significant differences between the species that correlate with differences in habitat spectral quality. We measured the spectral reflectance of the Dewlaps (colourful throat fans used in communication), and found that the A. cooki Dewlap reflects little ultraviolet (UV), while that of A. cristatellus reflects strongly in the UV. For both species downwelling light (irradiance) is rich in UV. However the background light (radiance) is rich in UV for A. cooki, but low in UV for A. cristatellus. Thus, the Dewlap of each species creates a high contrast with the background in the UV. Our findings strongly suggest that these two species are partitioning their habitat through specializations of the visual system and signal design to microhabitat light conditions.
Michael C. Moore - One of the best experts on this subject based on the ideXlab platform.
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Role of the adrenal gland in early post-hatching differentiation of alternative male phenotypes in the tree lezard (Urosaurus ornatus).
General and comparative endocrinology, 2004Co-Authors: David H. Jennings, Danika L. Painter, Michael C. MooreAbstract:During development, sex steroids are important in establishing differences between males and females. However, sex steroids also are involved in the development and maintenance of individual differences in morphology and behavior within each sex. As adults, male tree lizards (Urosaurus ornatus) exhibit alternative reproductive tactics correlated with Dewlap (throat fan) coloration. Males with orange-blue Dewlaps are aggressive and territorial, whereas males with orange Dewlaps are less aggressive and employ a satellite strategy. Dewlap coloration develops within the first 90 days after hatching and remains fixed throughout life. Recent work demonstrates that individual males differ in progesterone and testosterone secretion during development, suggesting that these hormones regulate the development of alternative male phenotypes. The current work uses in vitro incubation of adrenal and gonadal tissues to identify the source of progesterone and testosterone during the period of male differentiation and to follow ontogenetic changes in hormone release. The results indicate that, in all developmental stages sampled, adrenal incubations primarily contain progesterone and corticosterone whereas gonadal incubations contain primarily testosterone. These data indicate that the hatchling adrenal is the primary source of progesterone during early post-hatching development. Since progesterone has been demonstrated to play a role in the establishment of individual differences in morphology and behavior in male tree lizards, our results suggest that the hatchling adrenal gland plays an important role in post-hatching development of alternative male phenotypes.
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Population frequencies of alternative male phenotypes in tree lizards : geographic variation and common-garden rearing studies
Behavioral Ecology and Sociobiology, 1997Co-Authors: Diana K. Hews, Ignacio T. Moore, Christopher W. Thompson, Michael C. MooreAbstract:Tree lizards (Urosaurus ornatus) vary in throat fan (Dewlap) color. Earlier, we described five Dewlap types (Orange, Orange-Blue, Yellow, Yellow-Blue, and Blue), and reported that only males had blue in the Dewlap and that presence or absence of a discrete blue patch was correlated with male alternative reproductive phenotypes in a central Arizona population. Here, with a modified scheme characterizing two Dewlap elements, background color (orange, yellow, blue) and blue patch occurrence, we assessed: (1) sexual, annual, and geographic variation in the frequencies of Dewlap elements; (2) simple habitat correlates; and (3) the effects of laboratory rearing regime on Dewlap type. Within a population, frequencies of males and females expressing orange or yellow backgrounds did not differ, suggesting that control of background is similar in the sexes. Within several populations, frequencies of the Dewlap elements did not differ across years (and probably generations), indicating that phenotype frequencies are relatively stable. Among five populations frequencies of background colors varied, as did frequencies of male types (blue patch present or absent). Dewlap frequencies did not correlate with habitat (boulders or mesquite trees), although few populations were sampled. In male and female offspring reared from eggs to sexual maturity in a common-garden laboratory study, background color frequencies in both sexes and blue patch frequencies in males differed among offspring from different populations. Offspring frequencies matched respective parental population frequencies. Results suggest that among-population variation in frequencies of the two Dewlap elements are mediated by differences in genetics, in maternal effects, or both. Thus, differences in male behavior functionally linked to the blue patch also may be controlled by genetic or maternal effects.
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Syntopic Occurrence of Multiple Dewlap Color Morphs in Male Tree Lizards, Urosaurus ornatus
Copeia, 1991Co-Authors: Chris Thompson, Michael C. MooreAbstract:We describe a color polymorphism in male tree lizards, Urosaurus ornatus, that may be one of the most complex social badge polymorphisms known. Male tree lizards in central Arizona possess Dewlaps that are solid blue, solid yellow or solid orange, or bicolored consisting of a yellow or orange background with a blue central spot that varies continuously in size from a few scales to 55% of the area of the unextended Dewlap. The occurrence of this polymorphism varies geographically and microgeographically, from populations that are monomorphic, to those that are dominated by two Dewlap morphs, to those where all five morphs are more equally represented. Comparisons of the frequency of the different morph types both within and between years suggests no evidence of differential fitness between the morphs. Comparisons between habitats suggest that morph complexity was highest in the better quality habitat of the two sites we compared.
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Throat colour reliably signals status in male tree lizards, Urosaurus ornatus
Animal Behaviour, 1991Co-Authors: Christopher W. Thompson, Michael C. MooreAbstract:Abstract The use of small patches of colour, called badges, as signals of fighting ability (status signals) across age or sex classes has been well described. Examples of within age- or sex-class status signals are more poorly known. Most populations of adult male tree lizards, Urosaurus ornatus, are polymorphic in throat (Dewlap) colour within the same age class; Dewlap colour may be orange, yellow, or blue or bicolour combinations of an orange perimeter (background) surrounding a central blue spot that varies in size among individuals from 1 to 55% of the surface area of the unextended Dewlap. To test the hypothesis that the size of the central blue spot signals status among males, laboratory contests were staged between pairs of size-matched males for a limiting resource. Contests were staged between males that had Dewlaps with the (1) same background colour but different size central blue spots, and (2) same background colour and similar size central blue spots in which one male's Dewlap was painted orange and the other male's was painted orange with a large blue centre. In both experiments, encounters were dominated by the male with the larger central blue spot. These results support the hypothesis that the size per se of the central blue spot reliably signals fighting ability among males both within and across age classes. Furthermore, this is the first documented case of an inexpensive (badge) status signal that develops prior to sexual maturity and remains phenotypically unchanged during adult life.
Richard E. Glor - One of the best experts on this subject based on the ideXlab platform.
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Signals and Speciation: Anolis Dewlap Color as a Reproductive Barrier
Journal of Herpetology, 2017Co-Authors: Anthony J. Geneva, Sabina Noll, Richard E. GlorAbstract:Abstract The divergence of signals used in sexual selection and species recognition is thought to play an important role in speciation. As such, the striking diversity of Dewlap color in Anolis lizards may have contributed to the diversification of this species-rich group. Whether the Dewlap acts as a reproductive isolating barrier however remains unclear. We tested the prediction that the degree of Dewlap divergence between the two closely related and highly polymorphic Hispaniolan trunk anoles Anolis distichus and Anolis brevirostris is correlated with genetic divergence and the frequency of hybridization in nature. We use integrative analyses of Dewlap color variation and molecular genetics to investigate two pairs of localities where the species co-occur, including one pair of localities where the two species exhibit dissimilar Dewlaps and a second pair of localities where they have similar Dewlaps. At one site where species share similar Dewlap coloration, we found evidence of hybridization and lower...
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Comparative tests of the role of Dewlap size in Anolis lizard speciation
Proceedings. Biological sciences, 2016Co-Authors: Travis Ingram, Alexis Harrison, D. Luke Mahler, María Del Rosario Castañeda, Richard E. Glor, Anthony Herrel, Yoel E. Stuart, Jonathan B. LososAbstract:Phenotypic traits may be linked to speciation in two distinct ways: character values may influence the rate of speciation or diversification in the trait may be associated with speciation events. Traits involved in signal transmission, such as the Dewlap of Anolis lizards, are often involved in the speciation process. The Dewlap is an important visual signal with roles in species recognition and sexual selection, and Dewlaps vary among species in relative size as well as colour and pattern. We compile a dataset of relative Dewlap size digitized from photographs of 184 anole species from across the genus' geographical range. We use phylogenetic comparative methods to test two hypotheses: that larger Dewlaps are associated with higher speciation rates, and that relative Dewlap area diversifies according to a speciational model of evolution. We find no evidence of trait-dependent speciation, indicating that larger signals do not enhance any role the Dewlap has in promoting speciation. Instead, we find a signal of mixed speciational and gradual trait evolution, with a particularly strong signal of speciational change in the Dewlaps of mainland lineages. This indicates that Dewlap size diversifies in association with the speciation process, suggesting that divergent selection may play a role in the macroevolution of this signalling trait.
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Adaptive signal coloration maintained in the face of gene flow in a Hispaniolan Anolis Lizard.
BMC evolutionary biology, 2016Co-Authors: Alison G. Ossip-klein, Richard E. GlorAbstract:Studies of geographic variation can provide insight into the evolutionary processes involved in the early stages of biological diversification. In particular, multiple, replicated cases of geographic trait divergence present a powerful approach to study how patterns of introgression and adaptive divergence can vary with geographic space and time. In this study, we conduct replicated, fine-scaled molecular genetic analyses of striking geographic Dewlap color variation of a Hispaniolan Anolis lizard, Anolis distichus, to investigate whether adaptive trait divergence is consistently associated with speciation, whereby genetic divergence is observed with neutral markers, or whether locally adapted traits are maintained in the face of continued gene flow. We find instances where shifts in adaptive Dewlap coloration across short geographic distances are associated with reproductive isolation as well as maintained in the face of gene flow, suggesting the importance of both processes in maintaining geographic Dewlap variation. Our study suggests that adaptive Dewlap color differences are maintained under strong divergent natural selection, but this divergence does not necessarily lead to anole speciation.
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Inheritance data: Dewlap reflectance & percentage orange of year-old F1 & their fathers
2016Co-Authors: Audrey L. Kelly, Daniel J. Macguigan, Richard E. GlorAbstract:Reflectance data and percent orange of the Dewlap of year-old F1 & their fathers as measured in the lab for a common garden experiment assessing Dewlap color inheritance
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Dewlap color development data of F1s: Center Reflectance
2016Co-Authors: Audrey L. Kelly, Daniel J. Macguigan, Richard E. GlorAbstract:Dewlap reflectance of F1s taken as a time series during their development at 4, 6, 9 and 12 months of age
Manuel Leal - One of the best experts on this subject based on the ideXlab platform.
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visual playback of colorful signals in the field supports sensory drive for signal detectability
Current Zoology, 2018Co-Authors: Alex R Gunderson, Leo J Fleishman, Manuel LealAbstract:Colorful visual signals are important systems for investigating the effects of signaling environments and receiver physiology on signal evolution as predicted by the sensory drive hypothesis. Support for the sensory drive hypothesis on color signal evolution is mostly based on documenting correlations between the properties of signals and habitat conditions under which the signals are given (i.e., a correlational approach) and less commonly on the use of mathematical models that integrate representations of visual environments, signal properties, and sensory systems (i.e., a functional approach). Here, we used an experimental approach in the field to evaluate signal efficacy of colorful lizard throat fans called Dewlaps that show geographic variation in the lizard Anolis cristatellus. We used a remote controlled apparatus to display "fake Dewlaps" to wild lizards to test for adaptive divergence in Dewlap brightness (i.e., perceived intensity) among populations in situ. We found evidence of local adaptation in Dewlap brightness consistent with the sensory drive hypothesis. Specifically, Dewlaps that had the brightness characteristics of local lizards were more likely to be detected than those with the brightness characteristics of non-local lizards. Our findings indicate that simplified mathematical representations of visual environments may allow robust estimates of relative detectability or conspicuousness in natural habitats. We have shown the feasibility of evaluating color signal efficacy experimentally under natural conditions and demonstrate the potential advantages of presenting isolated components of signals to an intended receiver to measure their contribution to signal function.
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Why do Anolis Dewlaps glow? An analysis of a translucent visual signal
Functional Ecology, 2015Co-Authors: Leo J Fleishman, Brianna Ogas, David M. Steinberg, Manuel LealAbstract:Summary Male anoline lizards utilize a colourful, expandable throat fan, called the Dewlap, to rapidly and unambiguously signal their presence and species identity to conspecifics. Under some viewing conditions, the Dewlaps of some species appear to glow vividly, because they transmit a great deal of diffuse light, creating a translucent signal. Translucent signals are probably found in many animal groups, but they have rarely been studied. We hypothesized that Dewlap translucence might (i) increase Dewlap/background luminance contrast or (ii) increase the reliability of the colour as a species recognition signal by lowering the colour discrimination threshold in low light conditions such as forest shade. We calculated Dewlap colour (spectral radiance) for the Jamaican lizard Anolis lineatopus at natural perch sites with, and without, the inclusion of transmitted light. Transmitted light did not significantly increase the magnitude of luminance contrast between the Dewlap and background. We plotted colours of Dewlaps, background patches of habitat and Dewlaps of sympatric species in an anoline perceptual colour space (the colour tetrahedron), based on the four classes of cone photoreceptors found in the retina. Using a newly developed approach, we used ellipsoidal plots of uncertainty to quantify perceptual overlap between Dewlap spectral radiance and values for natural distractor colours. Diffuse transmission of light through the Dewlap greatly reduced the perceptual overlap between the Dewlap and natural background colours. This finding strongly suggests that selection has favoured the evolution of a translucent Dewlap as a mechanism to increase the reliability of detection of the signal under the low light conditions. In general, any animal's colour signal must emit sufficient light intensity to allow the colour to be discriminated from other distractor colours in the habitat. This will tend to favour the evolution of colours with higher total intensity (i.e. higher reflectance and/or transmittance) in animals that signal in relatively low light conditions such as forest shade.
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Habitat light and Dewlap color diversity in four species of Puerto Rican anoline lizards
Journal of Comparative Physiology A, 2009Co-Authors: Leo J Fleishman, Manuel Leal, Matthew H. PersonsAbstract:Closely related species often have signals that differ dramatically in design. The evolution of such differences may be important in the process of speciation. Selection for signal detectability under different habitat conditions has been proposed as a mechanism leading to the evolution of signal diversity. We examined Dewlap color in four closely related species of Anolis lizards that occupy habitats with different light conditions. Initially, we tested the hypothesis that lizards choose specific light conditions within each habitat in which to signal. We rejected this hypothesis for all four species. We next calculated the detectability of the Dewlap color of all four species at display locations in each habitat. If selection for detectability under the different light conditions explained the divergence in signal design, the occupant of a given habitat was predicted to have the highest signal detectability in that habitat. However, the rank order of detectability of the four Dewlap colors was nearly the same in all four habitats. We concluded that divergent selection for signal detectability does not, by itself, explain the evolution of Dewlap color diversity. We hypothesize that the evolution of Dewlap color diversity results from simultaneous selection for multiple functions of Dewlap color.
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differences in visual signal design and detectability between allopatric populations of anolis lizards
The American Naturalist, 2004Co-Authors: Manuel Leal, Leo J FleishmanAbstract:Abstract: We tested the prediction of the sensory drive hypothesis using four allopatric populations of the lizard Anolis cristatellus from two distinct environments (i.e., mesic and xeric conditions). For each population, we measured habitat light characteristics and quantified signal design by measuring the spectral and total reflectance and transmittance of the Dewlap. We used these data to calculate Dewlap detectability using an empirically based model of signal detection probability. We found that populations from mesic and xeric conditions occupy two distinct habitats with respect to light intensity and spectral quality and that Dewlap design has diverged between populations in a way that increases signal detectability in each habitat. The major difference in Dewlap design was in total reflectance and transmittance, making Dewlaps from xeric habitats darker and Dewlaps from mesic habitats brighter. Furthermore, Dewlap detection decreased significantly when a Dewlap from a xeric habitat is detected u...
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evidence for habitat partitioning based on adaptation to environmental light in a pair of sympatric lizard species
Proceedings of The Royal Society B: Biological Sciences, 2002Co-Authors: Manuel Leal, Leo J FleishmanAbstract:Terrestrial habitats exhibit a variety of light environments. If species exhibit evolutionary adaptations of their visual system or signals to habitat light conditions, then these conditions can directly influence the structure of communities. We evaluated habitat light characteristics and visual-signal design in a pair of sympatric species of lizards: Anolis cooki and Anolis cristatellus. We found that each species occupies a distinct microhabitat with respect to light intensity and spectral quality. We measured the relative retinal spectral sensitivity and found significant differences between the species that correlate with differences in habitat spectral quality. We measured the spectral reflectance of the Dewlaps (colourful throat fans used in communication), and found that the A. cooki Dewlap reflects little ultraviolet (UV), while that of A. cristatellus reflects strongly in the UV. For both species downwelling light (irradiance) is rich in UV. However the background light (radiance) is rich in UV for A. cooki, but low in UV for A. cristatellus. Thus, the Dewlap of each species creates a high contrast with the background in the UV. Our findings strongly suggest that these two species are partitioning their habitat through specializations of the visual system and signal design to microhabitat light conditions.
Tess Driessens - One of the best experts on this subject based on the ideXlab platform.
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Intraspecific Variation in the Information Content of an Ornament: Why Relative Dewlap Size Signals Bite Force in Some, But Not All Island Populations of Anolis sagrei.
Integrative and comparative biology, 2018Co-Authors: Simon Baeckens, Tess Driessens, Bieke Vanhooydonck, Katleen Huyghe, Raoul Van DammeAbstract:In many animals, male secondary sexual traits advertise reliable information on fighting capacity in a male-male context. The iconic sexual signaling device of anole lizards, the Dewlap, has been extensively studied in this respect. For several territorial anole species (experiencing strong intrasexual selection), there is evidence for a positive association between Dewlap size and bite capacity, which is an important determinant of combat outcome in lizards. Intriguingly, earlier studies did not find this expected correlation (relative Dewlap size-relative bite force) in the highly territorial brown anole lizard, Anolis sagrei. We hypothesize that the Dewlap size-bite force relationship can differ among populations of the same species due to interpopulation variation in the degree of male-male competition. In line with this thought, we expect Dewlap size to serve as a reliable predictor of bite performance only in those populations where the level of intrasexual selection is high. To tackle this hypothesis, we examined the relationship between male Dewlap size and bite force on the intraspecific level in A. sagrei, using an extensive dataset encompassing information from 17 island populations distributed throughout the Caribbean. First, we assessed and compared the relationship between both variables in the 17 populations under study. Second, we linked the relative Dewlap size-bite force relationship within each population to variation in the degree of intrasexual selection among populations, using sexual size dimorphism and Dewlap display intensity as surrogate measures. Our results showed that absolute Dewlap size is an excellent predictor of maximum bite force in nearly all A. sagrei populations. However, relative Dewlap size is only an honest signal of bite performance in 4 out of the 17 populations. Surprisingly, the level of signal honesty did not correlate with the strength of intrasexual selection. We offer a number of conceptual and methodological explanations for this unexpected finding.
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The brown anole Dewlap revisited: do predation pressure, sexual selection, and species recognition shape among-population signal diversity?
PeerJ, 2018Co-Authors: Simon Baeckens, Tess Driessens, Raoul Van DammeAbstract:Animal signalling structures are amongst the most variable characteristics, as they are subjected to a diversity of selection pressures. A well-known example of a diverse signalling system in the animal kingdom is the Dewlap of Anolis lizards. Dewlap characteristics can vary remarkably among and within species, and also between sexes. Although a considerable amount of studies have attempted to disentangle the functional significance of the staggering Dewlap diversity in Anolis, the underlying evolutionary processes remain elusive. In this study, we focus on the contribution of biotic selective pressures in shaping geographic variation in Dewlap design (size, colour, and pattern) and Dewlap display behaviour at the intraspecific level. Notably, we have tried to replicate and extend previously reported results hereof in both sexes of the brown anole lizard (Anolis sagrei). To do this, we assembled a dataset consisting of 17 A. sagrei heterogeneous island populations from the Caribbean and specifically tested whether predation pressure, sexual selection, or species recognition could explain interpopulational variation in an array of Dewlap characteristics. Our findings show that in neither males nor females estimates of predation pressure (island size, tail break frequency, model attack rate, presence of predatory Leiocephalus lizards) or sexual selection (sexual size dimorphism) could explain variation in Dewlap design. We did find that A. sagrei males from larger islands showed higher Dewlap display intensities than males from smaller islands, but the direct connection with predation pressure remains ambiguous and demands further investigation. Last, we could show indirect support for species recognition only in males, as they are more likely to have a 'spotted' Dewlap pattern when co-occurring with a higher number of syntopic Anolis species. In conclusion, we found overall limited support for the idea that the extensive interpopulational variability in Dewlap design and use in A. sagrei is mediated by variation in their biotic environment. We propose a variety of conceptual and methodological explanations for this unexpected finding.
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climate related environmental variation in a visual signalling device the male and female Dewlap in anolis sagrei lizards
Journal of Evolutionary Biology, 2017Co-Authors: Tess Driessens, Simon Baeckens, Manuela Balzarolo, Bieke Vanhooydonck, Katleen Huyghe, R. Van DammeAbstract:Animals communicate using a variety of signals that differ dramatically among and within species. The astonishing Dewlap diversity in anoles has attracted considerable attention in this respect. Yet, the evolutionary processes behind it remain elusive and have mostly been explored for males only. Here, we considered Anolis sagrei males and females to study signal divergence among populations. First, we assessed the degree of variation in Dewlap design (size, pattern, colour) and displays by comparing 17 populations distributed across the Caribbean. Second, we assessed whether the observed Dewlap diversity is associated to variation in climate-related environmental conditions. Results showed that populations differed in all Dewlap characteristics, with the exception of display rate in females. We further found that males and females occurring in ‘xeric’ environments had a higher proportion of solid Dewlaps with higher UV-reflectance. In addition, lizards inhabiting ‘mesic’ environments had primarily marginal Dewlaps showing high reflectance in red. For Dewlap display, a correlation with environment was only observed in males. Our study provides evidence for a strong relationship between signal design and prevailing environmental conditions, which may result from differential selection on signal efficacy. Moreover, our study highlights the importance of including females when studying Dewlaps in an evolutionary context. This article is protected by copyright. All rights reserved.
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Climate‐related environmental variation in a visual signalling device: the male and female Dewlap in Anolis sagrei lizards
Journal of evolutionary biology, 2017Co-Authors: Tess Driessens, Simon Baeckens, Manuela Balzarolo, Bieke Vanhooydonck, Katleen Huyghe, R. Van DammeAbstract:Animals communicate using a variety of signals that differ dramatically among and within species. The astonishing Dewlap diversity in anoles has attracted considerable attention in this respect. Yet, the evolutionary processes behind it remain elusive and have mostly been explored for males only. Here, we considered Anolis sagrei males and females to study signal divergence among populations. First, we assessed the degree of variation in Dewlap design (size, pattern, colour) and displays by comparing 17 populations distributed across the Caribbean. Second, we assessed whether the observed Dewlap diversity is associated to variation in climate-related environmental conditions. Results showed that populations differed in all Dewlap characteristics, with the exception of display rate in females. We further found that males and females occurring in ‘xeric’ environments had a higher proportion of solid Dewlaps with higher UV-reflectance. In addition, lizards inhabiting ‘mesic’ environments had primarily marginal Dewlaps showing high reflectance in red. For Dewlap display, a correlation with environment was only observed in males. Our study provides evidence for a strong relationship between signal design and prevailing environmental conditions, which may result from differential selection on signal efficacy. Moreover, our study highlights the importance of including females when studying Dewlaps in an evolutionary context. This article is protected by copyright. All rights reserved.
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Climatic and morphological data of Anolis sagrei populations
2017Co-Authors: Tess Driessens, Simon Baeckens, Manuela Balzarolo, Bieke Vanhooydonck, Katleen Huyghe, Raoul Van DammeAbstract:Descriptive statistics for Dewlap measurements in male and female brown anoles, with additional information on climatic variables of the populations sampled