Meeting Abstract
The genus Quadrula has long been a source of frustration for North American malacologists. This frustration stems from substantial interspecific morphological and distributional overlap which has created confusion over the validity of taxa. The most recent analysis (2019) proposed a decrease in species from five to three. No study has examined putative species across their geographic ranges sampling both mitochondrial and nuclear characters. We used multilocus molecular phylogenetics (COI, ND1, ITSI) to evaluate the taxonomic identity of all putative Quadrula taxa: Q. apiculata, Q. fragosa, Q. quadrula, Q. rumphiana as well as closely related species Tritogonia verrucosa and T. nobilis. We used >200 specimens from >50 localities to construct a robust phylogenetic hypothesis. We recovered monophyly of all but one species, Q. quadrula, which was paraphyletic in the ND1 gene tree analysis. Additionally, Q. apiculata, Q. rumphiana, and Q. quadrula clades 1 & 2 exhibited no differentiation at the nuclear locus. To test the hypothesis that mtDNA cladogenesis is indicative of speciation we integrated our Sanger-sequence dataset with nuclear wide restriction-site associated DNA sequencing (RADseq). We used micro-CT scanning and three-dimensional geometric morphometrics of Quadrula shells to quantify inter and intraspecific shell variation and compare this to our molecular results. We plan to leverage these results with museum shell material to infer the historic ranges of Quadrula species in North America, which is necessary for developing effective conservation strategies, especially for wide-ranging, highly variable species like those in the genus Quadrula.
