Taiwan's land-vertebrate suite: An assemblage forged by tectonism and sea-level shifts

Like many islands in continental-shelf settings, Taiwan has a rich land-vertebrate suite comprising mainly nonendemic taxa. Unusually, though, it also hosts a substantial fraction of endemic species, some the result of in situ diversification. Here, we disentangle the physical processes that have shaped the island's assemblage and document the roles they played. Taiwan is a high-elevation landmass on the edge of China's continental shelf, its emergence resulting from the ongoing collision between the Eurasian and Philippine Sea Plates, which started c . 5 Mya. For the first c . 4 Myr of the island's history colonizations involved over-water dispersal, hence relatively few establishment events. Significantly, the sizeable ecospace the incomers entered hosted a variety of niches (notably, greater than those in the areas they crossed from), and this spurred anagenesis and occasionally cladogenesis. Although the Pleistocene sea-level falls (starting c . 2.6 Mya) modified greatly and frequently the regional geography, only those occurring after 900 kya were sufficiently large (i.e., below −72/−75 m) to open up a succession of landbridges across the Taiwan Strait seabed to mainland Asia. Significantly, such episodes allowed taxa to enter Taiwan unimpeded, thereby accounting for the bulk of its lineages, most of which are nonendemic.