Convergent evolution in the territorial communication of a classic adaptive radiation: Caribbean Anolis lizards

To demonstrate adaptive convergent evolution, it must be shown that shared phenotypes have evolved independently in different lineages and that a credible selection pressure underlies adaptive evolution. There are a number of robust examples of adaptive convergence in morphology for which both these criteria have been met, but examples from animal behaviour have rarely been tested as rigorously. Adaptive convergence should be common in behaviour, especially behaviour used for communication, because the environment often shapes the evolution of signal design. In this study we report on the origins of a shared design of a territorial display among Anolis species of lizards from two island radiations in the Caribbean. These lizards perform an elaborate display that consists of a complex series of headbobs and dewlap extensions. The way in which these movements are incorporated into displays is generally species specific, but species on the islands of Jamaica and Puerto Rico also share fundamental aspects in display design, resulting in two general display types. We confirm these display types are convergent (the consequence of independent evolution on each island) and provide evidence that the convergence was driven by selection for enhanced signal efficiency. Our study shows how adaptation to common environmental variables can drive the evolution of adaptive, convergent signals in distantly related species.