Search

Morphological and physiological considerations suggest that sprinting ability and endurance capacity put conflicting demands on the design of an animal's locomotor apparatus, and therefore cannot be optimised simultaneously. To test this hypothesis, we correlated size-corrected maximal sprint speed and stamina of 12 species of lacertid lizards. Both raw species means and phylogenetically independent contrasts of sprint speed and stamina showed a significant negative relationship, giving support to the idea of an evolutionary trade-off between the two performance measures. To test the hypothesis that the trade-off is mediated by a conflict in morphological requirements, we correlated both performance traits with snoutvent length, size-corrected estimates of body mass and limb length, and relative hind limb length (the residuals of the relationship between hind and fore limb length). Fast running species had hind limbs that were long compared to their fore limbs. None of the other size and shape variables showed a significant relationship with speed or endurance. We conclude that the evolution of sprint capacity may be constrained by the need for endurance capacity and vice versa, but identification of the design conflict underlying this trade-off is needed to close the case.

Ecomorphological studies test the hypothesis of a tight correlation between an organism's morphology and its environment. Although this seems trivial, results are not unequivocal. In this study, we tested the ecomorphological hypothesis in three lacertid species from Corsica. Lacerta bedriagae, is a typical rock-dweller, occurring predominantly on vertical structures at high elevations, while Podarcis sicula inhabits areas with dense vegetation. The third species, Podarcis tiliguerta, is less conservative in its habitat use and some populations are syntopic with the other two species. We quantified habitat use in the field and tested whether the lizards preferred the same habitats under lab conditions. Furthermore, we determined maximal running and climbing speed, endurance and maneuverability. Different morphological features were measured. However, besides morphology, other traits (e.g. biochemistry, physiology) will influence performance. Since it is very difficult to assess the importance of such variables, we included limb kinematics (i.e. black box approach). The results indicate that the three species differ in habitat use and preference, performance and morphology as predicted by biomechanical models. Unexpectedly, the kinematical data cannot be linked to the observed variation in performance ability among species.

Sexual dimorphism may be indicative of differential natural and/or sexual selection pressures acting on males and females. Although similar degrees of adult sexual dimorphism may be observed among populations and species, underlying physiological, developmental and ecological processes driving growth during the juvenile stages may vary. Unraveling how and when differences arise during ontogeny is important to our understanding of the evolutionary patterns observed among adults. In addition, growth patterns may differ among traits within a single individual. A nolis lizards vary greatly in the degree of adult sexual size and shape dimorphism. Ultimate hypotheses (e.g. sexual selection, habitat partitioning) have been put forward to explain this variation, but proximate mechanisms operating during the juvenile stages remain largely unknown. Herein, we aim at elucidating the proximate mechanisms of sexual dimorphism in head and limb shape, performance and dewlap size in A nolis baracoae, a crown-giant anole. We used a longitudinal approach and raised 23 captive-bred juvenile A . baracoae lizards through adulthood. By quantifying body size, head and limb dimensions, dewlap size and bite performance, we obtained growth trajectories that were compared between the sexes and among traits. Our results show that the growth of head and limb shape is similar in males and females, whereas dewlap size and bite performance diverge at a specific age. Based on these results, we hypothesize that, whereas selection favors a similar head and limb shape in males and females, selection pressures on dewlap size and bite performance likely differ between the sexes. In addition, dewlap size starts diverging around the time the animals reach sexual maturity, whereas bite performance diverges much earlier in (sexually) immature males. [ABSTRACT FROM AUTHOR]

The idea that sexual signals should be honest signals of an animals intrinsic performance capacities is well established in behavioral ecology, but less information exists about whether the context of honest signaling changes with population structure. We investigated whether the context of honest signaling in green anole lizards (Anolis carolinensis) differs between two closely related, but highly divergent populations (a native swamp population and an enclosed campus population). Anoles in these two populations differ dramatically in habitat structure, display behavior, morphology, and escape behavior. We investigated whether the relative size of the dewlap (an extendable throatfan) in male green anoles was an honest indicator of relative bite force by collecting large samples of male lizards in the two populations. We collected data on both the intensity of predation pressure in the two habitats, as well as anole densities to ensure that differences in honest signaling were attributable to differences in habitat and consequently, social structure. We found that several aspects of sexual signaling differed between the populations, which we attributed to the greater potential for sexual selection in the enclosed Tulane population.

Elaborate sexual signals, such an deer horns or colorful elongated tail patches on birds, are considered hallmarks of the sexual selection process, and are thought to play a key role in influencing male reproductive success. However, while the size or color of such sexual signals can change across seasons in some animal species (e.g., birds), these changes are typically caused by endogenous hormonal rhythms. Male green anole lizards (Anolis carolinensis) possess large colorful throatfans that play a key role in territorial defense, and ultimately, reproductive fitness. We provide evidence that selection, driven in part by the presence of internal parasites, likely alters the relative size of the dewlap across seasons in these lizards. We show that the average male dewlap in spring is about 33% larger compared to similarly sized males in winter, and that dewlap size returns to its previous size the following spring. Mark-recapture studies show a marked turnover of about 90% of the adult males between Spring and Winter. This high mortality is driven in part by the presence of damaging internal parasites (larvae from a botfly) that infects male lizards at a much higher rate compared to females and juveniles. We propose that intense selection eliminates males with large dewlaps in the fall and winter, with younger large-dewlapped overwintering males replacing these eliminated males the following spring. Based on this dramatic morphological shift over such a short time span (> 8 months), we calculate that seasonal changes in dewlap size represent by far the most rapid case of natural selection ever documented.

As different life-history stages of a species potentially compete for the same prey, natural selection can be expected to give rise to intraspecific differences in morphology and performance that reduce intraspecific competition. Here we test whether different lifehistory stages and sexes differ in their head shape and size, bite forces and diet to test for reduced competition through niche divergence. Our results show that bigger lizards eat bigger and harder prey. Juveniles bite disproportionately hard for their size allowing them to eat relatively large prey. Moreover, males, females and juveniles differ significantly in their head size and shape as well as in the size and hardness of prey eaten. Multiple regression models indicate that head shape and size-corrected bite force are significantly correlated to prey size. Moreover, for a given prey size males tend to eat harder prey than females and juveniles. These data suggest that natural selection has shaped the ontogeny of head shape resulting in differential bite performance in juveniles, males and females of Anolis lineatopus. This allows animals of different sex and size classes to consume different prey, thus reducing intraspecific competition.

We compared external morphology, habitat use, and two performance abilities (clinging and biting) in two Louisiana populations of Anolis carolinensis lizards. One population (Good Hope Field) occurs in a freshwater swamp characterized by dense vegetation and numerous potential predators. The other population (Tulane University) is characterized by simple vegetation (primarily large leaves), and few potential predators. We sampled a large series of juvenile, female and male lizards in both habitats, and found that the two populations differ markedly in habitat use, biting performance, and size-adjusted limb dimensions. Tulane campus lizards occupied large leaves close to the ground, whereas Good Hope Field lizards used branches or the trunks of bushes and trees. Thus, Tulane lizards occurred on significantly lower and broader perches compared to Good Hope Field lizards. Tulane lizards tended to have relatively shorter limb dimensions, and also exhibited a significantly higher scaling coefficient for bite force (slope = 3.54 vs. 2.64 for Good Hope Field). By contrast, clinging ability did not differ significantly between populations. The unusually high bite forces of Tulane male lizards may have arisen as a consequence of increased male-male conflict, due to both the open nature of the habitat, and release from predators. However, our analyses do not reveal whether these interpopulational differences are plastic, or are a result of fixed genetic differences.

Secondary sexual traits are believed to function as signals of a males quality (i.e. mating success and survival). By investigating how the size or shape of a sexual trait relates to ecologically relevant performance measures, we can directly test whether a secondary sexual trait does represent a reliable cue. Furthermore, by measuring performance we can test whether natural selection and sexual selection pose conflicting demands on the same design trait. Anolis lizards are characterized by the possession of an extensible throat fan, or dewlap. Extensive variation exists in dewlap size and color among and within species. Although, it has been suggested that dewlap design might be important during male-male interactions, courtship, species recognition and predator encounters, it has not been tested whether relative dewlap size is a good indicator of performance. Here, we examine variation in relative dewlap size in Anolis carolinensis lizards. Over 400 individuals were sampled from a single lowland swamp population. We took measurements of dewlap size and performance (i.e. jump distance, acceleration capacity, clinging ability and bite force) on all individuals. We then tested whether relative dewlap size is a good predictor of the different performance traits and whether the four performance traits are inter-correlated. Size-corrected dewlap size appears to predict size-corrected bite force, while size-corrected clinging ability appears to be negatively correlated with size-corrected bite force. These data suggest that dewlap size is an honest indicator of an animals fighting ability and that bite force and clinging ability trade-off within A. carolinensis.

We describe polymerase chain reaction primers and amplification conditions for 13 highly polymorphic microsatellite DNA loci isolated from the Dalmatian wall lizard, Podarcis melisellensis. The number of alleles per locus ranged from 12 to 41, with levels of observed heterozygosity between 0.62 and 0.94. Most of these loci were successfully cross-amplified in the closely related species P. sicula, but levels of polymorphism were always lower. [ABSTRACT FROM AUTHOR]

The term terroir is used in viticulture to emphasize how the biotic and abiotic characteristics of a local site influence grape physiology and thus the properties of wine. In ecology and evolution, such terroir (i.e., the effect of space or "site") is expected to play an important role in shaping phenotypic traits. Just how important is the pure spatial effect of terroir (e.g., differences between sites that persist across years) in comparison to temporal variation (e.g., differences between years that persist across sites), and the interaction between space and time (e.g., differences between sites change across years)? We answer this question by analyzing beak and body traits of 4388 medium ground finches ( Geospiza fortis ) collected across 10 years at three locations in Galápagos. Analyses of variance indicated that phenotypic variation was mostly explained by site for beak size ( η 2  = 0.42) and body size ( η 2  = 0.43), with a smaller contribution for beak shape ( η 2  = 0.05) and body shape ( η 2  = 0.12), but still higher compared to year and site-by-year effects. As such, the effect of terroir seems to be very strong in Darwin's finches, notwithstanding the oft-emphasized interannual variation. However, these results changed dramatically when we excluded data from Daphne Major, indicating that the strong effect of terroir was mostly driven by that particular population. These phenotypic results were largely paralleled in analyses of environmental variables (rainfall and vegetation indices) expected to shape terroir in this system. These findings affirm the evolutionary importance of terroir, while also revealing its dependence on other factors, such as geographical isolation., Competing Interests: The authors declare no conflicts of interest., (© 2022 The Authors. Ecology and Evolution published by John Wiley & Sons Ltd.)

The ability of an animal to run fast has important consequences on its survival capacity and overall fitness. Previous studies have documented how variation in the morphology of the limbs is related to variation in locomotor performance. Although these studies have suggested direct relations between sprint speed and hindlimb morphology, few quantitative data exist. Consequently, it remains unclear whether selection acts in limb segment lengths, overall muscle mass or muscle architecture (e.g. muscle fiber length and cross-sectional area). Here, we investigate whether muscle architecture (mass, fiber length and physiological cross-sectional area), hindlimb segment dimensions, or both, explain variation in sprint speed across 14 species of Anolis lizards. Moreover, we test whether similar relationships exist between morphology and performance for both sexes, which may not be the case given the known differences in locomotor behavior and habitat use. Our results show that the main driver of sprint speed is the variation in femur length for both males and females. Our results further show sexual dimorphism in the traits studied and, moreover, show differences in the traits that predict maximal sprint speed in males and females. For example, snout vent length and overall muscle mass are also good predictors of sprint speed in males, whereas no relationships between muscle mass and sprint speed was observed in females. Only a few significant relationships were found between muscle architecture (fiber length, cross-sectional area) and sprint speed in male anoles, suggesting that overall muscles size, rather than muscle architecture, appears to be under selection., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2019. Published by The Company of Biologists Ltd.)

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.

When competing for food or other resources, or when confronted with predators, young animals may be at a disadvantage relative to adults because of their smaller size. Additionally, the ongoing differentiation and growth of tissues may constrain performance during early ontogenetic stages. However, juveniles must feed before they can become reproductively active adults and as such the adult phenotype may be the result of an ontogenetic filter imposing selection on juvenile phenotype and performance. Here we present ontogenetic data on head morphology and bite force for different lizard species. We test whether adults reflect selection on juveniles by comparing slopes of growth trajectories before and after sexual maturity in males and females and by examining the variance in head morphology and bite force in juveniles versus adults. Finally, we also present the first results of a selection study where animals were measured, marked and released, and recaptured the subsequent year to test whether head morphology and bite force impact survival., (© The Author 2016. Published by Oxford University Press on behalf of the Society for Integrative and Comparative Biology. All rights reserved. For permissions please email: journals.permissions@oup.com.)