First molecular phylogeny of the subfamily Polycerinae (Mollusca, Nudibranchia, Polyceridae)

The subfamily Polycerinae includes four genera with around 46 species described to date. This subfamily is characterized by a limaciform body, which may have simple tentacular processes on the margin of the oral veil. Phylogenetic relationships between the genera of the subfamily Polycerinae (Polyceridae) have not yet been studied, and therefore, the only available information is based on morphological descriptions. The present study reports the first phylogenetic analysis of Polycerinae based on the mitochondrial genes cytochrome oxidase subunit I and the large ribosomal subunit (16S rRNA) using maximum likelihood and Bayesian methods. Our results showed that Polycerinae is monophyletic, but the relationships within the subfamily as well as within Polycera remain unresolved. A key finding of this study is that there are clearly two sympatric species of Polycera present in South Africa: Polycera capensis Quoy and Gaimard, 1824 also found in Australia and an undescribed Polycera sp. On the other hand, the studied specimens of the genus Gymnodoris were clustered within Polycerinae, reopening the problem of the systematic position of this genus. Additional genes and species of Polycerinae and Gymnodoris would provide more information and probably fully resolve this situation.