Mitogenomic analyses shed new light on phylogenetic relationships within the genus Ruditapes (Bivalvia: Veneridae)

Ruditapes aspera is a member of the family Veneridae, the venus clams. This species is morphologically similar to other two globally economically important Ruditapes species, R. decussatus and R. philippinarum. Recent phylogenetic studies of Veneridae based on short DNA sequences have suggested that these species may be less closely related than originally thought. Relationships among species of Ruditapes clearly require further critical study. In this article, we show that the mitochondrial (mt) genome of R. aspera exhibits sex-linked heteroplasmy, that is doubly uniparental inheritance (DUI). Mitogenomic comparisons among three Ruditapes species showed that the features and gene arrangements of their mt genomes did not exhibit a high degree of similarity (this agrees with published data on other congeneric species of Veneridae) and that none of these species have a sister-group relationship with either of the other two species. These three species may belong to three different genera, but a fully revised classification will require considerable additional genomic and morphological data from a dense sampling of species and genera. Furthermore, we show that the pattern of relationships in our phylogeny of Ruditapes provides support for the polyphyletic origin of DUI.