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

<i>Anguispira kochi</i> (L. Pfeiffer, 1846), the banded tigersnail, is a North American member of the family Discidae. It is typically subdivided into two subspecies: <i>A. kochi kochi</i> (L. Pfeiffer, 1846) and <i>A. kochi occidentalis</i> (E. von Martens, 1882). Genetic data from throughout the distribution of <i>A. kochi</i> (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, <i>A. k. occidentalis</i>, 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 <i>A. occidentalis</i>. The status of other infraspecific taxa of both <i>A. kochi</i> and <i>A. occidentalis</i> is discussed, as well as the potential validity of subgenus Zonodiscus Pilsbry, 1948. Finally, the new classification of <i>Discus marmorensis</i> H.B. Baker, 1932 as <i>Anguispira marmorensis</i> (H.B. Baker, 1932) comb. nov. is proposed.