Cytochrome oxidase I-based phylogenetic relationships among the Pomatiopsidae, Hydrobiidae, Rissoidae and Truncatellidae (Gastropoda : Caenogastropoda : Rissoacea)

The Gondwanian-derived Asian pomatiopsid radiation is taxonomically complex , diversity-rich, and widely deployed geographically. This Asian branch of the family has coevolved with such human trematode parasites as Schistosoma and Paragonimus; it is ideally suitable for studying patterns and processe s of evolution over 100 million years. Cytochrome c oxidase subunit I gene sequences are used here to elucidate taxonomic relationships from the subsp ecies to familial level. In Chinese literature, pomatiopsid taxa have been classified in the Hydrobiidae; what are the genetic relationships between H ydrobia and allied taxa classified as pomatiopsid? Sixteen sequences, ranging in length from 578 to 645 nucleotides, are align ed from 11 species of nine genera assigned to seven families, four of which are rissoacean. Five different phylogenetic analyses are concordant: (1) t he pomatiopsid taxa are in one distinct clade, the other rissoaceans form a second clade; (2) truncatellids are more closely allied to the hydrobiids than to the pomatiopsids; (3) the rissoid Setia is part of the truncatellid -hydrobiid clade; (4) two subspecies of Oncomelania are clearly divergent, (5) triculine taxa appear divergent from pomatiopsine taxa. However, the Tr icula sp. node is weakly supported. Individuals of a population differ by an average of 0.005 +/- 0.004 nucleot ide differences/site; the subspecies of Oncomelania differ by 0.148 +/- 0.0 04; the two species of Hydrobia differ by 0.1 62 (range of 0.161 - 0.163); the triculine genera Tricula and Gammatricula differ by 0.132 (range of 0.1 30 - 0.133); the pomatiopsid subfamilies Pomatiopsinae and Triculinae diffe r by 0.179 +/- 0.020, the families Hydrobiidae and Pomatiopsidae differ by 0.267 +/- 0.016. Non-rissoacean and rissoacean taxa differ by 0.274 +/- 0.0 23.