Pleistocene speciation with and without gene flow in Euphaea damselflies of subtropical and tropical East Asian islands

Climatic oscillations during the Pleistocene period could have had a profound impact on the origin of tropical species by the alternation of allopatric isolation and inter-population gene flow cycles. However, whether tropical speciation involves strictly allopatric isolation, or proceeds in the face of homogenizing gene flow, is relatively unclear. Here, we investigated geographical modes of speciation in four closely-related Euphaea damselfly species endemic to the subtropical and tropical East Asian islands using coalescent analyses of a multi-locus data set. The reconstructed phylogenies demonstrated distinct species status for each of the four species and the existence of two sister species pairs, E. formosa/E. yayeyamana and E. decorata/E. ornata. The species divergence time of the sibling Euphaea damselflies dates back to within the last one Mya of the Middle to Lower Pleistocene. The speciation between the populous E. formosa of Taiwan and the less numerous E. yayeyamana of the ...