Systematic revision of the Japanese freshwater snail

Semisulcospira is a freshwater snail genus highly divergent in the ancient Lake Biwa, Japan, with history of ~4 million years. Although shell morphology, karyotype and molecular phylogeny have been well studied, systematic status several non-monophyletic species remains uncertain. In this study, we evaluated taxonomic accounts previously identified as decipiens, S. habei relatives. We examined genetic relationships using genome-wide SNP data elucidated morphological variation among these Random Forest classification. Morphological between name-bearing type decipiens newly collected specimens were also evaluated. characteristics effectively discriminated nine clusters, correlation morphology substrates was elucidated. revised habei, arenicola, nakasekoae ourensis synonymised multigranosa, yamaguchi, dilatata under fluvialis nakasekoae. described two new species, elongata sp. nov. cryptica nov., redefined phylogroups lacustrine niponica-group nakasekoae-group. Traits exhibiting intraspecific different flow velocity may indicate trophic adaptations. The habitat-related has certainly caused confusion species. drainage contributes to increasing diversity genus, generating ecological isolation riverine habitats. ZooBank: urn:lsid:zoobank.org:pub:A83B99F4-8709-4295-86B3-A6C595D65DA0