Meeting Abstract
Examining patterns of change in natural systems offers the opportunity to understand how biological diversity is both created and maintained. Bivalved scallops (Pectinidae) are a particularly good system to study evolutionary patterns of morphological change: they are a speciose clade, display an array of shell morphologies, are found in a wide range of habitats, and are broadly organized into five functional groups which vary in their level of mobility. Previous work has shown that scallops have strong convergent evolution in shell shape among unrelated long-distance swimming species. In this study, we characterized morphological patterns of shell shape in 121 species representing lineages from all functional groups to gain a more complete picture of the degree of morphological similarity among these groups. We combined morphological data on shell shape derived from landmark-based geometric morphometric methods with a phylomorphospace approach, a phylogenetic comparative method to infer evolutionary change along branches of a phylogeny. We evaluate the predictions that the scallop morphospace is partitioned according to shell morphologies defining the five functional groups. Our results find species of two of the five life-habits have evolved similar morphological shape from inhabiting similar environments at different geographic locations. We affirm convergent evolution of long-distance swimming among multiple lineages and find convergent evolution among species that are recessers (a burrowing behavior). Furthermore, our results find a striking trend of directional morphological evolution in one clade of recessers, along an axis that describes a progressively convex shell shape. We discuss these results in terms of the implications for understanding scallop biology and evolutionary history, and more broadly, in terms of evolutionary processes driving invertebrate diversity.
