The cichlid pharyngeal jaw novelty enhances evolutionary integration in the feeding apparatus.

The modified pharyngeal jaw system of cichlid fishes is widely viewed as a key innovation that substantially facilitated the evolutionary exuberance of this iconic evolutionary radiation. We conduct comparative phylogenetic analyses of integration, disparity, and rate of evolution among feeding-related, skeletal structures in Neotropical cichlids and North American centrarchids, which lack the specialized pharyngeal jaw. Contrasting evolutionary patterns in these two continental radiations, we test a classic decoupling hypothesis. Specifically, we ask whether the modified pharyngeal jaws in cichlids resulted in enhanced evolutionary independence of the oral and pharyngeal jaws, leading to increased diversity of trophic structures. Contrary to this prediction, we find significantly stronger evolutionary integration between the oral and pharyngeal jaws in cichlids compared to centrarchids, although the two groups do not differ in patterns of integration within each jaw system. Further, we find no significant differences between the two lineages in disparity or rates of morphological evolution. Our results suggest that the modified pharyngeal jaws resulted in less evolutionary independence of the feeding system, not greater independence as has long been thought. Thus, we raise the possibility that the cichlid novelty enhanced feeding performance, but did not substantially alter macroevolutionary dynamics within the feeding apparatus.