Meeting Abstract

SICB+    Adaptive radiation without independent stages of trait evolution in a lineage of Caribbean anoles Bodensteiner, BL*; Muñoz, MM; Yale University brooke.bodensteiner@yale.edu

Adaptive radiation encompasses diversification along multiple trait axes, producing phenotypically diverse, species-rich lineages. Yet, whether this phenomenon proceeds via independent or shared pulses of trait diversification remains unclear. Here, we simultaneously investigated morphological (body size and limb dimensions) and physiological (heat and cold tolerance) evolution in the adaptive radiation of anole lizards from the Caribbean island of Hispaniola. Rates and patterns of morphological and physiological diversity are largely unaligned, belying independent selective pressures associated with structural and thermal niches. Contrary to expectation, most traits exhibited no exceptional pulses of diversification, evolving instead via a purely Brownian process. The lone exception, cold tolerance, exhibits a rapid ‘late burst’ of diversification, reflecting invasion of high-elevation environments, rather than niche partitioning within communities. Heat tolerance evolution, in contrast, evolves more slowly than the other traits, and reflects behavioral buffering, particularly in edge-habitat species (a pattern associated with the Bogert effect). In contrast to the nearby island of Puerto Rico, closely related anoles do not partition thermal niche space: instead, separation across biogeographic boundaries serves to keep ecologically similar, closely-related anoles apart. Despite a strong conceptual basis for discrete stages of adaptive radiation, independence in rates and patterns of trait evolution is not mirrored by independent pulses of diversification. The high diversity of this island radiation accumulated largely as a by-product of time and historical biogeography, with surprisingly few exceptional pulses of trait evolution.