Tempo-spatial evolution of seed plant endemism in Taiwan island

Aim: In Taiwan island, recent land-bridge and oversea dispersal after the appearance of proto-Taiwan (<6.5 Ma) is responsible for its biodiversity assembly. Radiations have also been widely reported in mountain systems. The tempo-spatial route to the floral hotspot was determined through a meta-analysis of the evolution of endemic plants. Location: Taiwan island and its adjacent regions. Taxon: Seed plants. Methods: Published dated phylogenies were compiled to infer the origin times represented by the stem ages. To determine the speciation mode, either in situ origin or dispersal origin, the ancestral range shift pattern and/or current distribution range of the sister taxa were used with 10 different biogeographical regions classified. Histograms quantifying the numbers of different origin modes within bins of 0.5 Ma were constructed. Probabilities of long-distance dispersal (LDD) were evaluated. Results: The 125 sampled species originate between the late Eocene and late Pleistocene, of which 14 (11.2%) and 111 (88.8%) were derived before and after the emergence of proto-Taiwan, respectively. Spatially, in situ speciation would have a bigger contribution to the formation of endemism than dispersal events (56.8% vs. 43.2%). The species with in situ origin (mean = 1.83 Ma) were significantly younger than those with dispersal origin (mean = 6.34 Ma). The main regions where dispersal occurred were South-Central China (n = 29) and Southeast China (n = 28), followed by Japan (n = 14). High probabilities (60.8%) of LDD were found. Main Conclusions: Spatially, recent land-bridge and oversea dispersal from the adjacent Asian flora is supported and the southern part of China was found to be the most important source. In situ speciation that may have correlated with mountain uplift, monsoon intensification and Pleistocene climatic fluctuations exerted greater contributions to the biodiversity there. Temporally, floral endemism predominantly occurred after the emergence of proto-Taiwan. Additional investigations with more sophisticated sampling and genetic data are needed in the future.

Automated summary

In Taiwan, the biodiversity assembly is mainly attributed to land-bridge and oversea dispersal after the emergence of proto-Taiwan. In situ speciation plays a greater role in the formation of endemism compared to dispersal events. The southern part of China is found to be the most important source for dispersal, with South-Central China and Southeast China as the main regions. Species with in situ origin are younger than those with dispersal origin. Further investigations with more sophisticated sampling and genetic data are required in the future.