Phytogeographic aspects of Lysionotus pauciflorus sensu lato (Gesneriaceae) in the China, Japan and Taiwan regions: phylogenetic and morphological relationships and taxonomic consequences

Comparison of leaf morphometric variation and phylogenetic analyses based on nrITS and partial trnC-D cpDNA sequences were conducted for samples of Lysionotus pauciflorus sensu lato collected from China, Japan and Taiwan. In the morphometric comparison, leaves of plants from Japan proper and those from Taiwan proper were not significantly distinguishable by their leaf length to width ratio. In phylogenetic analyses, monophyly of L. pauciflorus s. l. samples was strongly supported, and Japanese and Taiwanese samples fell into a clade separate from Chinese samples. In the Japan–Taiwan clade, plants from Japan proper formed a sister clade to those from Okinawa Island (Japan) and Taiwan. The present results suggest that (1) the L. pauciflorus s. l. samples from China, Japan and Taiwan must be treated as a single species; (2) L. pauciflorus s. l. originated in China; (3) a single dispersal event, dispersal via a land-bridge during low sea levels in a Pleistocene glacial maximum, from China to Taiwan and Japan is proposed; (4) three oversea dispersal events, probably through anemochory, to Japan proper, across the Tokara Gap, to Okinawa islands crossing the Kerama Gap, and from Taiwan to Lanyu Island are proposed. The study gives further insight into the biogeographical dynamics between the Ryukyus and surrounding areas.