Data from: 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 Yaeyama islands occurred despite significant
bidirectional, asymmetric gene flow, which is strongly inconsistent with a
strictly allopatric model. In contrast, speciation of the approximately
equal-sized populations of E. decorata of the south-east Asian mainland
and E. ornata of Hainan is inferred to have involved allopatric divergence
without gene flow. Our findings suggest that differential selection of
natural or sexual environments is a prominent driver of species divergence
in subtropical E. formosa and E. yayeyamana; whereas for tropical E.
decorata and E. ornata at lower latitudes, allopatric isolation may well
be a pivotal promoter of species formation.