Long-distance dispersal from island to island: colonisation of an oceanic island in the vicinity of the Asian continent by the land snail genus Karaftohelix (Gastropoda: Camaenidae)

Ullung Island is an oceanic island in the Sea of Japan about 130 km distant from the Korean peninsula. The biota of this oceanic island is thought to be derived from the closest continental region while the importance of long-distance dispersal from other areas for the formation of the Ullung Island biota was considered negligible. In this study, we have examined the origin of the Ullung Island-endemic land snail Karaftohelix adamsi (Kuroda & Hukuda, 1944) using a molecular phylogenetic approach with two mitochondrial (COI and 16S rRNA) and nuclear (ITS regions) DNA sequences. Our results revealed that K. adamsi has originated from the northernmost region of the Japanese archipelago or Sakhalin Island, most likely from Rebun Island of Hokkaido, by long-range dispersal across a distance of 1200 km. This finding reveals that the biota of the oceanic Ullung Island has not exclusively originated from the Asian mainland, but that some elements have originated from the more distant archipelago of Japan and the Far East of Russia.