Ectothermic species are particularly sensitive to changes in temperature and may adapt to changes in thermal environments through evolutionary shifts in thermal physiology or thermoregulatory behaviour. Nevertheless, the heritability of thermal traits, which sets a limit on evolutionary potential, remains largely unexplored. In this study, we captured brown anole lizards () from two populations that occur in contrasting thermal environments. We raised offspring from these populations in a laboratory common garden and compared the shape of their thermal performance curves to test for genetic divergence in thermal physiology. Thermal performance curves differed between populations in a common garden in ways partially consistent with divergent patterns of natural selection experienced by the source populations, implying that they had evolved in response to selection. Next, we estimated the heritability of thermal performance curves and of several traits related to thermoregulatory behaviour. We did not detect significant heritability in most components of the thermal performance curve or in several aspects of thermoregulatory behaviour, suggesting that contemporary selection is unlikely to result in rapid evolution. Our results indicate that the response to selection may be slow in the brown anole and that evolutionary change is unlikely to keep pace with current rates of environmental change.

Given that sexual signals are often expressed more highly in one sex than the other, they can impose a sex-specific cost of reproduction through parasitism. The two primary paradigms regarding the relationship of parasites to sexual signals are the good genes hypothesis and the immunocompetence handicap hypothesis; however, there are other ecological, morphological and energetic factors that might influence parasite infections in a sex-specific fashion. We tested the relationship between expression of a sexual signal (the dewlap) and ecological, morphological and energetic factors mediating ectoparasite (mite) load between male and female Panamanian slender anoles (Anolis apletophallus). We found that males were more highly parasitized than females because of the preponderance of ectoparasites on the larger dewlap of males. Indeed, ectoparasite infection increased with both body size and dewlap size in males but not in females, and parasite infection was related to energy storage in a sex-specific fashion for the fat bodies, liver and gonads. Our work and previous work on testosterone in anoles suggests that this pattern did not arise solely from immunosuppression by testosterone, but that mites prefer the dewlap as an attachment site. Thus, the expression of this sexual signal could incur a fitness cost that might structure life-history trade-offs.

The selective pressures exerted by predation can have considerable influence on the behavior of prey species across a wide range of taxa. Within a species, this force may differ between the sexes, leading to sex‐specific behavioral responses to predators. We tested whether the black spiny‐tailed iguana Ctenosaura similis is able to use auditory cues to detect an avian predator and whether antipredator responses differ in a sex‐dependent fashion. We conducted behavioral assays in which a food item was used as bait while iguanas were subjected to a recording of a Harris's hawk or white noise as a control. We found that a significantly greater percentage of individuals of either sex responded to the hawk call than to the white noise. We also found that a significantly greater percentage of females than males responded to either sound. These results suggest that not only do black spiny‐tailed iguanas incorporate auditory cues into predator detection, but that antipredator behavioral responses differ between the sexes as well. Such sex‐specific behaviors can be attributed to morphological and endocrine differences between male and female iguanas. These findings may also lend insight into how behavior can influence the evolution of sexual dimorphism within a species.