The biomechanical basis of evolutionary change in a territorial display

1. Few studies have examined how the anatomy of an animal signal contributes to, or limits, the evolution of signal differentiation among closely related species. 2. In Anolis lizards, adult males extend a large, conspicuous dewlap as part of a territorial advertisement display. Males of species from the island of Jamaica rely on the rapid extension of the dewlap to facilitate display detection by territorial neighbours and conspecific females. Males of other species on the island of Puerto Rico extend the dewlap at considerably slower speeds and instead rely on other strategies to maintain an effective display. What initially prompted this divergence in display between the islands is unknown, but evidence suggests that it may have something to do with the way the dewlap is extended during display. 3. Our goal was to determine whether an innovation in the dewlap lever in Jamaican lineages, but absent in Puerto Rican lineages, accounted for the evolution of the high-speed dewlap on Jamai...