Meeting Abstract
Geographic variation typically coincides with differences in local selection pressures, leading to broad patterns of phenotypic variation in widespread species. In several species, variation in morphological and ecological traits in particular is often associated with differences in elevation or latitude, or both. Here, we use data collected on 15 populations of the ornate tree lizard (Urosaurus ornatus) in southern Arizona that differ in elevation and latitude to evaluate patterns of geographic variation in key morphological (body size, head shape) and ecological (diet) traits linked with fitness. Overall, we show that body size declined with increasing elevation, and these patterns differed by sex. Conversely, we did not detect any latitudinal variation in body size. Jointly, these findings support a greater role of elevation in driving body size evolution in U. ornatus, in terms of both overall adult size and magnitude of sexual size dimorphism. With respect to head shape, lizard jaw length declined with both increasing latitude and elevation, suggesting that other ecological factors might be involved in driving variation in this trait. To that end, previous work in our lab with U. ornatus has demonstrated that head shape can inform variation in diet in this species, which may explain our observed patterns of jaw length in this study. Currently, tissue samples from these lizards are being processed for their carbon and nitrogen stable isotope content. We plan to use these results to test whether these observed geographic patterns in morphology are concomitant with differences in diet. Ultimately, via inclusion of these isotopic data with our current findings, we will provide important insight into the factors driving phenotypic variation in this widespread species.
