Evolutionary Patterns of Anolis Lizard Skulls: An Investigation in Geometric Morphometrics and an Educational Exploration of Structure and Function

This study explores the evolutionary patterns of Anolis lizard skulls and integrates findings into a curriculum focused on elucidating the structure and function of a lizard's head. The first objective was to develop an understanding of how the evolutionary patterns, of an extraordinary group of lizards (Anolis) compares to their relatives. Most of the prior research on Anolis morphology has focused on the post-cranium because of its significance towards subdivision of the arboreal habitat. But the group’s remarkable diversity in head shape has been seriously under-investigated. By performing geometric morphometric analysis of skull shape across a large sample of anoles and relatives, we found that Anolis lizards occupy a unique area and a wider region of morphological space compared to the 11 other families examined in this study. This extraordinary amount of skull diversity arose through a distinct mode of evolution compared to relative groups; anoles moved into novel regions of morphospace by relatively large morphological transitions. The second objective was designing a module for students to investigate the structure and function of lizard heads. The goal is for students to understand how head shape (structure) differs between two species of anoles – one with a short face (Anolis sagrei), and one with a long face (Anolis maynardi), and how differences in head structure influence bite strength (function). The students will work with a data set that I collected on Cayman Brac, where both these species can be found, to develop skills such as forming questions, collecting, and analyzing data, proposing explanations based on evidence, and communicating those explanations.