Molecules & morphology reveal ‘new’ divergent, widespread Lampsiline species (Bivalvia: Unionidae)

Abstract

The recognition of biodiversity in imperiled groups of organisms is fundamental to their conservation. In the Family Unionidae, the greatest radiation of freshwater mussels, species descriptions have been misled by extreme intraspecific shell variation and conversely interspecific conchological stasis. Lampsilis teres (Rafinesque, 1820) a polymorphic, widespread species has historically been split into as many as three subspecies that correlate to phenotypic variants. Recently, one subspecies was elevated to species level based on unique morphology and molecular differences. However, other subspecies designations are no longer recognized and no study has investigated these phenotypes with molecular characters. In this study I characterize the morphology of two phenotypes of L. teres using geometric and traditional morphometrics and use molecular phylogenetics to test the hypothesis that phenotypes represent separate species. Results from my molecular analyses unanimously indicate that L. teres as it is currently recognized is made up of two divergent, non-sister species. Herein I redescribe Lampsilis anodontoides (Lea, 1831) and use morphometrics and machine-learning algorithms to characterize shell morphology variation in each taxon.