Author: edagostino

At the 2019 Evolution Meetings thus far, we’ve seen some excellent work on anoles’ interaction with, and adaptation to, our changing world. Vincent Farrallo gave a talk on modeling the (surprising) effects on climate change on anole species, and Bailey Howell presented a poster on how Anolis cristatellus‘ toepads differ in shape and size between urban and non-urban environments.

In Monday’s poster session, Chris Thawley, a postdoctoral fellow in Jason Kolbe’s lab at the University of Rhode Island who will be teaching at Davidson College in the fall, gave a great contribution to this body of presentations at the meeting. His poster, “Cities in the spotlight: Does tolerance of artificial light at night promote urban invasions?”, showed his detailed work on this “evolutionarily novel condition.” He predicted artificial light at night, or ALAN, would be a double-edged sword for anoles. On the one hand, it perturbs sleep and endocrine cycles, makes it easier to for predators to find an anole late-night snack, and may negatively impact reproduction. It might not necessarily be all negative, however, as it could make it easier for anoles to find food and mates and protect territories.

Chris found significant effects of ALAN on reproductive habits: anoles exposed to ALAN start to lay eggs earlier and lay more eggs than anoles facing natural lighting conditions. Further, ALAN increases anole growth! Interestingly enough, however, Chris found that anoles have no real preference between ALAN and natural lighting conditions, and don’t appear to be more or less stressed under ALAN. In addition to this work with live anoles, Chris searched the literature to see if there’s an overlap between anole species that are invasive and those that have been reported to take advantage of ALAN. There is indeed such an overlap — 7 species are invasive but aren’t known to use ALAN and 8 non-invasive species use ALAN, but there are 15 invasive ALAN-using anole species!

Chris’s next questions involve the effect of ALAN on other taxa, as well as whether urbanizing anole species have adaptations that make them predisposed to take advantage of ALAN and what the effects of plasticity are in doing so. Given the prevalence of artificial light at night, and our love of Anolis, it should prove really exciting to learn more about the interaction between the two!

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!