A molecular phylogeny of Physidae (Gastropoda : Basommatophora) based on mitochondrial DNA sequences

Abstract

The family Physidae (Pulmonata: Basommatophora) is a group of freshwater hermaphroditic snails that have a Holarctic distribution with extension into Central and South America. Despite considerable literature justifying various taxonomic schemes and groupings, no classification has been proposed using modern phylogenetic methods. In an effort to expand what is known concerning the evolutionary relationships of Physidae, we examined a portion of the mitochondrial 16S rRNA and cytochrome c oxidase subunit I genes among 66 specimens representing 28 taxa. The molecular phylogeny based on mitochondrial sequences supports the monophyly of the family Physidae. Six major clades were uncovered in the analysis, corresponding to differences in penial morphology. These six groups include the following recommended phylogenetic species and species groups: Aplexa elongata (Say), Aplexa 1 group; Physa marmorata Guilding, Aplexa 3 group; P. fontinalis (Linneaus), P. jennessi Dall and P. vernalis Taylor & Jokinen, type a group; P. gyrina Say and P. ‘ancillaria ’ Say, type b group; P. acuta Draparnaud, P. spelunca Turner & Clench, P. species A and P. zionis Pilsbry, type c group; and P. pomilia Conrad and P. hendersoni Clench, type bc group