Data from: Trait decoupling promotes evolutionary diversification of the trophic and acoustic system of damselfishes

Trait decoupling, wherein evolutionary release of constraints permits specialisation of formerly integrated structures, represents a major conceptual framework for interpreting patterns of organismal diversity. However few empirical tests of this hypothesis exist. A central prediction, that the tempo of morphological evolution and ecological diversification should increase following decoupling events, remains inadequately tested. In damselfishes (Pomacentridae), a cerato-mandibular ligament links the hyoid bar and lower jaws, coupling two main morpho-functional units directly involved in both feeding and sound production. Here we test the decoupling hypothesis by examining the evolutionary consequences of the loss of the cerato-mandibular ligament in multiple damselfish lineages. As predicted, we find that rates of morphological evolution of trophic structures increased following the loss of the ligament. However, this increase in evolutionary rate is not associated with an increase in trophic breadth but rather with morpho-functional specialisation for the capture of zooplanktonic prey. Lineages lacking the cerato-mandibular ligament also show different acoustic signals (i.e. higher variation of pulse periods) from others, resulting in an increase of the acoustic diversity across the family. Our results support the idea that trait decoupling can increase morphological and behavioural diversity through increased specialisation rather than the generation of novel ecotypes.