Collaborative Research: A Functional Perspective on Adaptive Radiation: Explaining Differences in the Adaptive Radiations of Mainland and Island Anolis Lizards

Harvard University, Cambridge MA

Investigators

Abstract

Adaptive radiation, in which a clade diversifies from an ancestral form to produce descendants adapted to utilize a wide variety of ecological niches, has become a topic of great recent interest. The evolutionary radiation of Anolis lizards in the Caribbean has become a textbook case study of adaptive radiation, demonstrating that independent radiations can converge on very similar adaptive traits. This project expands this work to ask why in some cases evolutionary diversification yields very different results. On each island in the Greater Antilles, evolutionary radiation has occurred, producing species specialized to use different parts of the habitat (e.g., twigs, grass, canopy). Amazingly, evolution has occurred independently on each island, producing the same set of habitat specialists. Detailed analysis has indicated that strong relationships exist among species between anatomy and habitat use. Long-legged species occur on broad surfaces, for example, and more arboreal species have better developed toepads. Functional studies have explained these relationships by determining the relationship between morphology and functional performance capabilities, on one hand, and between performance abilities and habitat use and behavior, on the other. Anolis has also radiated widely in mainland Central and South America. Although less studied, these lizards have clearly evolved in different ways. Mainland anoles are as diverse among themselves as are island anoles, but the mainland species differ anatomically from the islands species. Most strikingly, the relationship between anatomy and habitat use differs fundamentally between mainland and island anoles. The PIs will investigate whether differences in the anatomy~ecology relationship result because the relationship between functional capabilities and ecology differ or because the relationship between anatomy and functional capabilities differs (or both). In addition, the PIs will seek explanations for the variation in anatomy~performance relationships between island and mainland lizards, focusing on the physiological properties of muscles. Jointly the data collected to address these goals will enable the PIs to address the question of why mainland anoles have radiated in fundamentally different ways than island anoles. Undergraduate students, including women and individuals from underrepresented groups, a postdoctoral fellow and foreign collaborators will receive unique interdisciplinary training. The PIs will work with the Harvard Museum of Natural History to develop an exhibit on Anolis as a model system for understanding how evolution works.