Molecular Phylogeny Of Stylommatophora (Mollusca), Inferred By ITS-2, Partial 5.8S And Partial 28S RDNA In RDNA Gene-cluster

The phylogeny of Stylommatophora (Gastropoda: Euthynerua) was inferred based on the partial 5.8s, ITS-2 and partial 28S rDNA sequence data, which was statistically described and aligned before phylogenetic analysis. The nucleotide substitution pattern showed by the data set made the choice of a complex nucleotide substitution model GTR+I+Γ. Both the Bayesian method and ML method were employed in the present phylogenetic analysis. The result indicated that all the stylommatophoran members, exnear-to-root Succineidae, were located within one clade supported by 100% posterior probability. Monophyletic Orthurethra was supported by 86% posterior probability, built a clade as (((Partulidae, (Pupillidae, (Orculidae, Pyramidulidae)), (Buliminidae, Valloniidae)), (Vertiginidae, Cochlicopidae)), Chondrinidae). Two remaining stylommatophoran suborders Sigmurethra and Heterurethra were not monophyletically supported. In Stylommatophora, all the superfamilies were paraphyletic or polyphyletic; all the families, excluding polyphyletic Camaenidae, Subulinidae, Partulidae, Helicarionidae, Vitrinidae and Zonitidae, were more or less monophyletically featured. Based on the present result, some questions, including the phylogenetic relationship between prosobranchs and pulmonates, polyphyletic orgination of slugs and semi-slugs, and so on, were discussed.