Phylogenomic analyses reveal a single deep-water colonisation in Patellogastropoda

Patellogastropoda, the true limpets, is a major group of gastropods widely distributed in marine habitats from the intertidal to deep sea. Though important for understanding their evolutionary radiation, the phylogenetic relationships among the patellogastropod families have always been challenging to reconstruct, with contradictory results likely due to insufficient sampling. Here, we obtained mitogenomic and phylogenomic data (transcriptomic or genomic) from six species representing the three predominantly deep-water patellogastropod families: Lepetidae, Neolepetopsidae, and Pectinodontidae. By using various phylogenetic methods, we show that mitogenome phylogeny recovers monophyly of eight families in most of the trees, though the relationships among families remain contentious. Meanwhile, a more robust family-level topology consistent with morphology was achieved by phylogenomics. This also reveals that these mainly deep-water families are monophyletic, suggesting a single colonisation of the deep water around the Jurassic. We also found a lack of significant correlation between genome size and habitat depth, despite some deep-water species exhibiting larger genome sizes. Our phylogenomic tree provides a stable phylogenetic backbone for Patellogastropoda that includes seven of the nine recognized families and paves the way for future evolutionary analyses in this major group of molluscs.