115.5 Saturday, Jan. 7 Variation in circulating steroid hormones among Caribbean Anolis ecomorphs HUSAK, J.F.*; LOVERN, M.B.; Univ. of St. Thomas; Oklahoma State Univ. email@example.com
The evolutionary processes leading to adaptive radiations have been intensely studied, yet the proximate mechanisms leading to phenotypic change during these speciation events have received less attention. Anolis lizards of the Caribbean are a classic example of an adaptive radiation, with each Greater Antillean island having independently evolved similar sets of coexisting ecomorphs. In addition to the well-documented convergence of morphology within ecomorphs, ecomorphs also appear to have convergently evolved similar mating systems and social organizations, though this remains poorly studied. A likely mediator for this behavioral variation is testosterone. Testosterone affects a range of male attributes, including rates of behavior and intensity of physical engagement with rival males. We predicted that ecomorphs would differ in testosterone consistent with social behavior differences. We also predicted that species of the same ecomorph category on different islands would have relatively similar testosterone levels. That is, trunk-ground anoles should have high testosterone levels compared to twig anoles on an island, with other ecomorphs being intermediate, and this pattern should be repeated across islands. We compared eight species within five ecomorphs from the Bahamas and Jamaica, finding significant differences among species in male and female testosterone levels. Even though the rank order of testosterone levels for the ecomorphs was not as we predicted, the order among ecomorphs was consistent across islands. When looking across species, we found no correlation between testosterone levels and corticosterone levels for males or females, but we did find a significant correlation between male and female testosterone levels across species. We further examined evolutionary relationships between testosterone levels and sexual dimorphism in size, shape, and performance.