Evolution 2019: How Does Urbanization Affect Toepad Shape and Size in Anolis cristatellus?

Bailey Howell, a rising senior in Travis Hagey‘s lab at Mississippi University for Women, presented a poster at Evolution on differences in toepad morphology between urban and non-urban populations of Anolis cristatellus. The two of them coauthored the work with Kristin Winchell, who has been investigating morphological effects of urbanization in that species, and who captured A. cristatellus for the study. Bailey mapped their toepad landmarks and quantified a suite of toepad traits, including length and width, in a whopping 160 of them! She did this to investigate differences between individuals from urban and non-urban sites, with the goal of contributing to our understanding of the species’ adaptation to cities.

She ran some neat statistics for the project: first, a principal component analysis of all toepads scanned, which found differences in the degree to which urban and non-urban toepads are bent. She went one step further by running a canonical variate analysis to find which factors are maximally different between the urban and non-urban lizards. A scaled (pun unintended) figure from her poster of the theoretical most-urban and most-non-urban toepads is below (urban is in gray, non-urban is in green).

This CVA explained significant variation between the two populations, and accounted for 14.5% of the difference! Taking things a step further, Bailey analyzed size as well as shape from the traits she measured, and saw that urban toepads were wider, and, in particular, longer, than non-urban ones. Next steps for the project include adding more toepads to the dataset, analyzing the data in light of more (toepad and non-toepad) traits in these individuals, and looking for an effect on performance. It seems like they’re well on their way to understanding this important effect of urbanization in this species!