Prodigious polyphyly in Pleuroceridae (Gastropoda: Cerithioidea)

Abstract

Phylogenomic studies with hundreds or thousands of loci are rare for most invertebrate groups, including freshwater gastropods. This can prevent understanding of phylogeny, which hinders many areas of research. Pleuroceridae is a family of freshwater snails that is highly imperiled and plays an essential role in the ecology of many freshwater systems of the eastern United States. However, the evolutionary history of the family is not understood, and the systematics of the family has not been revised in a modern framework. Pleurocerids display a variety of egg-deposition behaviors and shell shapes, making the family an ideal system for studying evolution of invertebrate life history and morphology. However, past mitochondrial-based phylogenetic analyses have failed to produce meaningful phylogenetic hypotheses, preventing conclusions about pleurocerid systematics and evolution. Here, we generated a novel anchored hybrid enrichment probe set with phylogenetic utility for Pleuroceridae. We sampled pleurocerids from across their range to test the probe set and generated a backbone phylogeny. Our analyses uncovered striking levels of polyphyly among currently accepted genera. Numerous species were also polyphyletic, indicative of unrecognized diversity. Phylogenetic patterns also revealed considerable convergence of shell morphologies. In contrast, anatomical and life history features appeared to be much less homoplastic. Despite generic paraphyly, high support for most major clades and phylogenetic cohesiveness of non-shell characters indicate utility of the AHE probe set for studying pleurocerid evolution.