Denser mitogenomic sampling improves resolution of the phylogeny of the superfamily Trochoidea (Gastropoda: Vetigastropoda)

The great morphological and ecological diversity within the superfamily Trochoidea s. l. has in the past hindered the reconstruction of a robust phylogeny for the group based on morphology. Moreover, previous molecular phylogenies have disagreed on the monophyly and internal relationships of Trochoidea s. l., as well as on its relative phylogenetic position within Vetigastropoda. In order to further resolve the trochoidean and vetigastropod phylogenetic trees, we considerably increased the representation of trochoidean families for which no previous mitochondrial (mt) genomes were available: the complete mt genome of Cittarium pica (Tegulidae) and the nearly complete mt genomes of Tectus virgatus (Tegulidae), Gibbula umbilicaris (Trochidae) and Margarites vorticiferus (Margaritidae) were sequenced. In addition, the nucleotide sequences of all protein-coding and ribosomal RNA genes of Clanculus margaritarius (Trochidae) and of Calliostoma zizyphinum (Calliostomatidae) were derived from transcriptomic sequence data. The phylogenetic trees were reconstructed using probabilistic methods with Neomphalina as outgroup; these recovered with maximal support a clade of Trochoidea sensu Hickman & McLean (1990, Nat. Hist. Mus. Los Angeles County Sci. Series, 35: 1-169), which included superfamilies Angarioidea and Phasianelloidea deeply nested within superfamily Trochoidea sensu Williams (2012, Zool. Scripta, 41: 571-595). The families Trochidae + Calliostomatidae were the sister group to the remaining trochoidean lineages. Of these, the family Margaritidae was sister to a clade including Phasianelloidea + Angarioidea and Turbinidae + Tegulidae, this latter family being paraphyletic (Cittarium and Tectus need to be assigned to a new family). Gene order within the newly determined mt genomes was very stable (with only a few rearrangements, restricted to transfer RNA genes) and conformed to the vetigastropod and gastropod consensus genome organizations.