Mosaic evolution of the skull in labrid fishes involves differences in both tempo and mode of morphological change

Modularity is a ubiquitous feature of organismal design that plays an important role in structuring patterns of morphological diversification. Modularity can facilitate evolutionary changes by allowing subsets of traits to coevolve as integrated units and follow quasi-independent evolutionary trajectories, a pattern that may be particularly consequential in the case of highly complex morphological structures. Here we examine modularity in a complex and highly kinetic structure, the teleost skull, and ask if a modular organization of the skull has influenced the diversification dynamics of the shapes of its osteological components across the labrid phylogeny. We compiled one of the largest three-dimensional morphological datasets of fishes to date, and used geometric morphometrics to quantify patterns of cranial shape evolution across 184 species of wrasses (Labridae). We then tested several hypotheses of modularity inspired by functional and developmental relationships between cranial b...