Integrative taxonomy confirms the synonymy of three springsnail species (Hydrobiidae: Pyrgulopsis)

The small, spring-dwelling snails, Pyrgulopsis Call & Pilsbry, 1886, form a diverse radiation in Western North America. In this study, we examine the validity of three species of Pyrgulopsis, Pyrgulopsis pilsbryana (Baily & Baily, 1952), P. nonaria Hershler, 1998, and P. transversa Hershler, 1998. These three species of Pyrgulopsis are found primarily in Utah, with ranges extending into Idaho, Wyoming, and Nevada. They were originally diagnosed primarily on the number and position of penial glands, but subsequent examination with mitochondrial DNA data suggested they should be synonymized. Here, we incorporate additional mitochondrial and nuclear DNA data, increased geographic sampling, and quantify some stated differences in shell and radula morphology. We test the utility of penial ornamentation and other anatomical features used to distinguish these species. We found that the shell shape and radula features measured tend to be unique to each local population, not species-specific distinguishing features. Further, we found the diagnostic features used to erect the three focal species are not associated with phylogenetic relationships. Therefore, we present a synonymy of the three focal species under the name with priority, P. pilsbryana.