Distribution patterns of vines within the East Asian island chain

Abstract

The northward dispersal of thermophilic plants along the East Asia island chain is influenced by cold stress, strait barrier and island effect. However, the impact of each parameter is not clear. In this study, we try to clarify the contribution of the above three effects to the geographical patterns of cold-intolerant climbing plants (vines) within the East Asia island chain. We divided the East Asian region into inland, coastal and island chain belts (Belt I, II and III, respectively), and 13/14 latitudinal regions. Distribution patterns of taxa shared by two adjacent belts were compared. We evaluated the impacts of cold stress effects by comparing the northern-most distribution boundary of vines within the island chain with those on the East Asian mainland and matching average January temperature isotherms. We assessed the strait barrier effect by comparing it with non-strait biogeographic lines. The island effect was assessed by quantifying the percentage of discontinuously distributed taxa. The results showed that: The northern-most limit of 54.3% of genera and 63.2% of species shared by Belts II and III coincided with a strait, with 27.2% of genera and 25.0% of species being discontinuously distributed. Cold stress, island effect and strait barrier effects together explained the patterns of 82.1% of genera and 87.7% of species shared by Belts II and III, which was higher than the value explained by cold stress on the mainland (77.7% and 72.4%, respectively). Cold stress, island effect and strait barrier explained 29.6%, 13.6% and 38.9% distribution patterns of taxa at the genus level, and 25.0%, 16.4% and 46.3% at the species level, respectively. Distribution patterns that could not be explained by cold stress were explained by strait barrier and island effect along the East Asian island chain. The East Asian island chain, especially the Ryukyu Islands, might be an efficient avenue for the northward dispersal of terrestrial plants, explaining the low degree of endemism and prevalence of discontinuously distributed taxa in this region.