Biomechanics Shed Light On Differences In Signal Behaviour

Why do closely related species sometimes differ in signalling behaviour, despite apparent similarities in the selection pressures that act on the signal? That question is addressed in a paper in Functional Ecology now available as an early view.

Comparing Anolis species from Jamaica that extend the dewlap rapidly with more slowly extending relatives from Puerto Rico, Ord, Collar and Sanger have modelled the performance of the dewlap and then simulated changes to the system to predict its effects on the speed of the dewlap extension. The predictions are then compared with data on both morphology from cleared and stained specimens and actual dewlap speeds for lizards recorded in the field.

The analyses show that morphological changes have affected the performance of the dewlap display in Jamaican and Puerto Rican anoles differently. Within islands structural changes have led to differences in dewlap speed among species, whereas differences between islands are the result of an increase in muscle contraction velocity present in Jamaican species, but absent in Puerto Rican species.

The study is an excellent example of how investigations into the biomechanics of motion-based visual displays can increase our understanding of differences in signal behaviour.