A phylogenomic backbone for gastropod molluscs

Gastropods have survived several mass extinctions during their
evolutionary history resulting in extraordinary diversity in morphology,
ecology, and developmental modes, which complicate the reconstruction of a
robust phylogeny. Currently, gastropods are divided into six subclasses:
Caenogastropoda, Heterobranchia, Neomphaliones, Neritimorpha,
Patellogastropoda, and Vetigastropoda. Phylogenetic relationships among
these taxa historically lack consensus, despite numerous efforts using
morphological and molecular information. We generated sequence data for
transcriptomes derived from twelve taxa belonging to clades with little or
no prior representation in previous studies in order to infer the deeper
cladogenetic events within Gastropoda and, for the first time, infer the
position of the deep-sea Neomphaliones using a phylogenomic approach. We
explored the impact of missing data, homoplasy, and compositional
heterogeneity on the inferred phylogenetic hypotheses. We recovered a
highly supported backbone for gastropod relationships that is congruent
with morphological and mitogenomic evidence, in which Patellogastropoda,
true limpets, are the sister lineage to all other gastropods
(Orthogastropoda) which are divided into two main clades (i)
Vetigastropoda s.l. (including Pleurotomariida + Neomphaliones) and (ii)
Neritimorpha + (Caenogastropoda + Heterobranchia). As such, our results
support the recognition of five subclasses (or infraclasses) in
Gastropoda: Patellogastropoda, Vetigastropoda, Neritimorpha,
Caenogastropoda and Heterobranchia.