A split decision: molecular and biogeographical evidence support species-level status of Anguispira kochi and Anguispira occidentalis (Stylommatophora, Discidae)

Anguispira kochi (L. Pfeiffer, 1846), the banded tigersnail, is a North American member of the family Discidae. It is typically subdivided into two subspecies: A. kochi kochi (L. Pfeiffer, 1846) and A. kochi occidentalis (E. von Martens, 1882). Genetic data from throughout the distribution of A. kochi (sensu lato) was used to produce a phylogenetic analysis and, together with morphological and distributional data, assess the taxonomic status of its subspecies. Evidence for elevating the western subspecies, A. k. occidentalis, to the rank of species level is provided and the implications this change has for the conservation status (and future conservation plans) of both species is discussed. A lectotype is designated for A. occidentalis. The status of other infraspecific taxa of both A. kochi and A. occidentalis is discussed, as well as the potential validity of subgenus Zonodiscus Pilsbry, 1948. Finally, the new classification of Discus marmorensis H.B. Baker, 1932 as Anguispira marmorensis (H.B. Baker, 1932) comb. nov. is proposed.