Rapid parallel morphological and mechanical diversification of South American Pike Cichlids (Crenicichla)
Burress, Edward (2022), Rapid parallel morphological and mechanical diversification of South American Pike Cichlids (Crenicichla), Dryad, Dataset, https://doi.org/10.25338/B8XP7D
Explosive bouts of diversification are one of the most conspicuous features of the tree of life. When such bursts are repeated in similar environments it suggests some degree of predictability in the evolutionary process. We assess parallel adaptive radiation of South American pike cichlids (Crenicichla) using phylogenomics and phylogenetic comparative methods. We find that species flocks in the Uruguay and Iguazú River basins rapidly diversified into the same set of ecomorphs that reflect feeding ecology. Both adaptive radiations involve expansion of functional morphology, resulting in unique phenotypes in terms of jaw shape, size, and protrusion. Yet, form and function were decoupled such that most ecomorphs share similar mechanical properties or the jaws (i.e., jaw motions during feeding). Prey mobility explained six to nine-fold differences in the rate of morphological evolution, but had no effect on the rate of mechanical evolution. We find no evidence of gene flow between species flocks or with surrounding coastal lineages that may explain their rapid diversification. When compared to cichlids of the East African Great Lakes and other prominent adaptive radiations, pike cichlids share many themes, including rapid morphological expansion, specialization along the benthic-to-pelagic habitat and soft-to-hard prey axes, and the evolution of conspicuous functional innovations. Yet, decoupled evolution of form and function and the absence of hybridization as a catalyzing force are departures from patterns observed in other adaptive radiations.