Molecular phylogeny of the western North American pebblesnails, genus Fluminicola (Rissooidea: Lithoglyphidae), with description of a new species

Abstract

The northwestern North American freshwater gastropod genus Fluminicola (Caenogastropoda, Lithoglyphidae) was previously hypothesized to be paraphyletic based on morphologic data, with F. virens positioned outside the clade containing other congeners. We further evaluated the phylogenetic relationships of Fluminicola using mitochondrial cytochrome c oxidase subunit I (COI) gene sequence data from 22 of 24 previously described congeners, a new congener (F. gustafsoni) that closely resembles F. virens morphologically, representatives of four other lithoglyphid genera, and several outgroups. A Bayesian analysis resolved two well supported Fluminicola clades, consistent with morphological heterogeneity. The clade composed of F. virens and F. gustafsoni was sister to the rest of the Lithoglyphidae; the clade containing the remaining congeners was sister to Somatogyrus. Our results confirm that Fluminicola is paraphyletic. However, this genus cannot be revised until the phylogenetic relationships of its possibly extinct type species are resolved. The new species described herein, F. gustafsoni, differs from F. virens in its smaller size, medium-convex and prominently shouldered teleoconch whorls, weakly angled shell aperture, presence of a well-developed rectangular wing on the outer marginal radular teeth, vertically oriented coiled oviduct, and in its COI sequences. Fluminicola gustafsoni is distributed in riverine habitats in the lower Snake River watershed.