Taxonomic revision of Aegista subchinensis (Mollendorff, 1884) (Stylommatophora, Bradybaenidae) and a description of a new species of Aegista from eastern Taiwan based on multilocus phylogeny and comparative morphology

Aegista subchinensis (Mollendorff, 1884) is a widely distributed land snail species with morphological variation and endemic to Taiwan. Three genetic markers (partial sequence of the mitochondrial cytochrome c oxidase subunit I [COI], the 16S rDNA and the nuclear internal transcribed spacer 2 [ITS2]) were analysed to infer phylogenetic relationships and genetic divergence of closely related species of the genus Aegista, A. vermis (Reeve, 1852) and A. oculus (Pfeiffer, 1850). A new species from A. subchinensis has been recognized on the basis of phylogenetic and morphological evidences. The nominal new species, A. diversifamilia sp. n. is distinguished from A. subchinensis (Mollendorff, 1884) by its larger shell size, aperture and apex angle; wider umbilicus and flatter shell shape. The northernmost distribution of A. diversifamilia sp. n. is limited by the Lanyang River, which is presumed to mark the geographic barrier between A. diversifamilia sp. n. and A. subchinensis.