Evidence for an outcrossing reproductive strategy in the hermaphroditic heterobranch gastropod Valvata utahensis (valvatidae), with notes on the genetic differentiation of V. utahensis and V. humeralis

Abstract

The hermaphroditic aquatic heterobranch Valvata utahensis is a federally endangered snail endemic to the Snake River corridor in southern Idaho, USA. Although an appreciable understanding of molluscan taxonomic diversity has been established within this ecosystem, little is currently known about the ecology and life history of many individual species (V. utahensis included). In this study, we used a combined analysis of mitochondrial and nuclear genetic variation within V. utahensis to infer the predominant mode of reproduction (selfing vs outcrossing) within natural populations of this species. Results of this analysis indicated that outcrossing is likely a common reproductive strategy. We discuss our results in the context of conservation and management efforts for this endangered species. Furthermore, in the course of performing our investigations, we frequently collected specimens that were tentatively identified as V. humeralis. Given that little genetic work has previously been performed within the genus Valvata, we compared genetic data from V. utahensis with data from V. humeralis to determine whether molecular data supported morphological evidence that these two taxa are distinct evolutionary entities. Results of our analyses clearly revealed strong patterns of genetic differentiation between these two taxa and confirmed the presence of two sympatric Valvata species within the Snake River system.