Mate choice tests provided no evidence of prezygotic reproductive isolation between a population of Physa virgata (Gould, 1855) collected from its type locality in the Gila River of Arizona and Physa acuta (Draparnaud, 1805) from a control site in Charleston, South Carolina. Reared in a no-choice experimental design, 10 outcross Arizona × South Carolina pairs initiated reproduction at approximately the same age as Arizona × Arizona controls, and earlier than South Carolina × South Carolina controls. Parents in the outcross experiment did not differ significantly from either control in their median weekly fecundity across 10 weeks of observation, yielding an F₁ generation with significantly improved viability. We detected no evidence of reduction in F₁ fertility. Thus, P. virgata, the most widespread freshwater gastropod of the American Southwest, should be considered a junior synonym of the cosmopolitan P. acuta.