Phylogenetic positions of some genera and species of the family Buccinidae (Gastropoda: Mollusca) from China based on ribosomal RNA and COI sequences

A phylogenetic analysis of members of the family Buccinidae was conducted using 18S rRNA gene, 28S rRNA gene and the mitochondrial cytochrome oxidase I gene. We studied 18 species of Buccinidae that belong to eight different genera and inhabit the China coastal seas. We analyzed the patterns of divergence between an outgroup and basal ingroup taxa, the monophyly of the genus Neptunea, and the position of one unnamed species within the Buccinidae. A phylogenetic tree (neighbor-joining (NJ) method) was reconstructed based on the sequences of 18S rRNA, 28S rRNA and COI, with Rapana venosa as outgroup. The NJ tree indicated that the 18 species could be divided into five groups. The genus Buccinum was monophyletic, whereas Neptunea was shown to be paraphyletic since it included Siphonalia subdilatata and Neptunea sp., a new species. This novel species otherwise clustered consistently with Neptunea cumingi in three other phylogenetic trees, showing a low genetic distance and divergence percentage of sequences belonging to the genus Neptunea. A smaller genetic distance and a smaller difference of 18S rRNA, 28S rRNA and COI sequences between Neptunea cumingii and Neptunea arthritica cumingii confirmed them to be the same species.