Body shape diversification along the benthic-pelagic axis in marine fishes

Colonization of novel habitats can result in marked phenotypic responses to the new environment that include changes in body shape and opportunities for further morphological diversification. Fishes have repeatedly transitioned along the benthic-pelagic axis, with varying degrees of association with the substrate. Previous work focusing on individual lineages shows that these transitions are accompanied by highly predictable changes in body form. Here, we generalize expectations drawn from this literature to study the effects of habitat on body shape diversification across 3,344 marine teleost fishes. We compare rates and patterns of evolution in eight linear measurements of body shape among fishes that live in pelagic, demersal, and benthic habitats. While average body shape differs between habitats, these differences are subtle compared to the high diversity of shapes found within each habitat. Benthic living increases the rate of body shape evolution and has led to numerous lineages ...