ABSTRACT
If fitness optima for a given trait differ between males and females in a population, sexual dimorphism may evolve. Sex-biased trait variation may affect patterns of habitat use, and if the microhabitats used by each sex have dissimilar microclimates, this can drive sex-specific selection on thermal physiology. Nevertheless, tests of differences between the sexes in thermal physiology are uncommon, and studies linking these differences to microhabitat use or behavior are even rarer. We examined microhabitat use and thermal physiology in two ectothermic congeners that are ecologically similar but differ in their degree of sexual size dimorphism. Brown anoles (Anolis sagrei) exhibit male-biased sexual size dimorphism and live in thermally heterogeneous habitats, whereas slender anoles (Anolis apletophallus) are sexually monomorphic in body size and live in thermally homogeneous habitats. We hypothesized that differences in habitat use between the sexes would drive sexual divergence in thermal physiology in brown anoles, but not slender anoles, because male and female brown anoles may be exposed to divergent microclimates. We found that male and female brown anoles, but not slender anoles, used perches with different thermal characteristics and were sexually dimorphic in thermal tolerance traits. However, field-active body temperatures and behavior in a laboratory thermal arena did not differ between females and males in either species. Our results suggest that sexual dimorphism in thermal physiology can arise from phenotypic plasticity or sex-specific selection on traits that are linked to thermal tolerance, rather than from direct effects of thermal environments experienced by males and females.
Footnotes
Competing interests
The authors declare no competing or financial interests.
Author contributions
Conceptualization: M.L.L., C.L.C.; Methodology: M.L.L.; Formal analysis: M.L.L., A.J.S., K.M.K., K.L.C.; Investigation: M.L.L., L.K.N., D.J.N., A.J.S., C.L.M., A.K.C., J.D.C., A.A.R., I.M., E.F., C.E.W., B.C., M.A.G.K., D.J.P.P., C.H.F., S.M.A., Z.A.G., C.L.C.; Resources: M.L.L., W.O.M., J.B.L., C.L.C.; Data curation: M.L.L.; Writing - original draft: M.L.L.; Writing - review & editing: L.K.N., D.J.N., A.J.S., C.L.M., A.K.C., J.D.C., K.M.K., A.A.R., I.M., E.F., C.E.W., B.C., M.A.G.K., D.J.P.P., C.H.F., S.M.A., K.L.C., Z.A.G., W.O.M., J.B.L., C.L.C.; Supervision: M.L.L., W.O.M., J.B.L., C.L.C.; Project administration: M.L.L., D.J.N., K.L.C., W.O.M., J.B.L., C.L.C.; Funding acquisition: M.L.L., L.K.N., D.J.N., A.K.C., J.D.C., A.A.R., W.O.M., J.B.L., C.L.C.
Funding
Funding for this project was provided by a Smithsonian Institution Biodiversity Genomics Postdoctoral Fellowship and a Smithsonian Tropical Research Institute Earl S. Tupper Postdoctoral Fellowship awarded to M.L.L., a Smithsonian Institution Scholarly Studies Grant awarded to M.L.L. and W.O.M., a Smithsonian Predoctoral Fellowship and NERC studentship (NE/L002485/1) awarded to D.J.N., American Museum of Natural History Theodore Roosevelt Memorial Grants awarded to A.K.C. and J.D.C., Georgia Southern University Graduate Student Development Grants awarded to A.K.C., J.D.C. and A.A.R., and a Smithsonian Short-Term Fellowship awarded to A.K.C. This project was also made possible through the support of a grant from the John Templeton Foundation to J.B.L. (the opinions expressed in this publication are those of the authors and do not necessarily reflect the views of the John Templeton Foundation).
- Received August 17, 2020.
- Accepted December 7, 2020.
- © 2021. Published by The Company of Biologists Ltd
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