A Phylogenetic Overview of the Genus Vertigo O. F. Müller, 1773 (Gastropoda: Pulmonata: Pupillidae: Vertigininae)

Abstract

ABSTRACT We document global phylogenetic pattern in the pupillid land snail genus Vertigo by analyses of nDNA (ITS1 and ITS2) and mtDNA (CytB and 16S) sequence from 424 individuals representing 91 putative specific and subspecific Vertigo taxa. nDNA and mtDNA data were separately subjected to neighbor-joining, minimum evolution, maximum likelihood and Bayesian reconstruction methods, with conclusions being drawn from shared topological structures. Six highly supported, reciprocally monophyletic subgeneric level clades were identified: Vertigo, Alaea, Boreovertigo new subgenus, Isthmia, Staurodon and Vertilla. 88 species or subspecies were also confirmed, nine of which are new and formally described herein: V. beringiana, V. chiricahuensis, V. chytryi, V. genesioides, V. kodamai, V. kurilensis, V. lilljeborgi vinlandica, V. pimuensis and V. pisewensis. Thirteen taxa were synonymized: V. arthuri basidens, V. arthuri hubrichti, V. arthuri paradoxa (= V. arthuri); V. allyniana (= V. modesta); V. andrusiana (= V. columbiana); V. conecuhensis (= V. alabamensis); V. dedecora tamagonari (= V. dedecora); V. elatior, V. idahoensis (= V. ventricosa); V. eogea (= V. ovata); V. modesta insculpta (= V. modesta concinnula), V. modesta microphasma, V. modesta sculptilis (= V. modesta castanea). Qualitative observations of conchological features, ecological preferences and geographic coverage were conducted for each subgenus and genetically supported species or subspecies-level taxon. These demonstrated that: (1) a suite of diagnostic shell features usually exists to demarcate each species-level taxon; (2) shell features were incapable of defining genetically validated subgenera; (3) all subgenera had transcontinental ranges; (4) ⅓ of all species possess continental or trans-continental ranges, with very few having range extents < 1,000 km; (5) all subgenera and fully ⅔ of global Vertigo species and subspecies are found in North America, more than 2.5 times the number found in central and eastern Asia, the second most diverse region. This is similar to several other molluscan groups, such as the polygyrid land snails and unionid bivalves for which North America is the global biodiversity hotspot.