Contingency and Determinism in Replicated Adaptive Radiations of Island Lizards

TLDR

Historical contingencies predict that repeated evolutionary radiations will yield disparate outcomes even from similar starting conditions. The study tested whether Anolis lizards radiating on the four Greater Antillean islands would produce divergent outcomes. The authors examined Anolis radiations across the four Greater Antillean islands. Morphometric and phylogenetic analyses show that the same ecomorphs evolved independently on each island, indicating that adaptive radiation can overcome historical contingencies to produce similar outcomes.

Abstract

The vagaries of history lead to the prediction that repeated instances of evolutionary diversification will lead to disparate outcomes even if starting conditions are similar. We tested this proposition by examining the evolutionary radiation of Anolis lizards on the four islands of the Greater Antilles. Morphometric analyses indicate that the same set of habitat specialists, termed ecomorphs, occurs on all four islands. Although these similar assemblages could result from a single evolutionary origin of each ecomorph, followed by dispersal or vicariance, phylogenetic analysis indicates that the ecomorphs originated independently on each island. Thus, adaptive radiation in similar environments can overcome historical contingencies to produce strikingly similar evolutionary outcomes.