Abstract
BackgroundPleistocene glacial oscillations have significantly affected the historical population dynamics of temperate taxa. However, the general effects of recent climatic changes on the evolutionary history and genetic structure of extant subtropical species remain poorly understood. In the present study, phylogeographic and historical demographic analyses based on mitochondrial and nuclear DNA sequences were used. The aim was to investigate whether Pleistocene climatic cycles, paleo-drainages or mountain vicariance of Taiwan shaped the evolutionary diversification of a subtropical gossamer-wing damselfly, Euphaea formosa.ResultsE. formosa populations originated in the middle Pleistocene period (0.3 Mya) and consisted of two evolutionarily independent lineages. It is likely that they derived from the Pleistocene paleo-drainages of northern and southern Minjiang, or alternatively by divergence within Taiwan. The ancestral North-central lineage colonized northwestern Taiwan first and maintained a slowly growing population throughout much of the early to middle Pleistocene period. The ancestral widespread lineage reached central-southern Taiwan and experienced a spatial and demographic expansion into eastern Taiwan. This expansion began approximately 30,000 years ago in the Holocene interglacial period. The ancestral southern expansion into eastern Taiwan indicates that the central mountain range (CMR) formed a barrier to east-west expansion. However, E. formosa populations in the three major biogeographic regions (East, South, and North-Central) exhibit no significant genetic partitions, suggesting that river drainages and mountains did not form strong geographical barriers against gene flow among extant populations.ConclusionsThe present study implies that the antiquity of E. formosa's colonization is associated with its high dispersal ability and larval tolerance to the late Pleistocene dry grasslands. The effect of late Pleistocene climatic changes on the subtropical damselfly's historical demography is lineage-specific, depending predominantly on its colonization history and geography. It is proposed that the Riss and Würm glaciations in the late Pleistocene period had a greater impact on the evolutionary diversification of subtropical insular species than the last glacial maximum (LGM).
Highlights
Pleistocene glacial oscillations have significantly affected the historical population dynamics of temperate taxa
It is proposed that the Riss and Würm glaciations in the late Pleistocene period had a greater impact on the evolutionary diversification of subtropical insular species than the last glacial maximum (LGM)
The antiquity and colonization history of E. formosa could be due to the flying ability of the adult and larval tolerance to the periodically dry grassland habitats that characterized Pleistocene land bridges
Summary
Pleistocene glacial oscillations have significantly affected the historical population dynamics of temperate taxa. The general effects of recent climatic changes on the evolutionary history and genetic structure of extant subtropical species remain poorly understood. The aim was to investigate whether Pleistocene climatic cycles, paleo-drainages or mountain vicariance of Taiwan shaped the evolutionary diversification of a subtropical gossamer-wing damselfly, Euphaea formosa. Climatic oscillations of the Pleistocene period have significantly affected the population dynamics and genetic structures of extant taxa. Land bridges between Taiwan and the adjacent Asian continent formed and submerged intermittently during Pliocene and Pleistocene glacial cycles owing to changes in sea levels [9,10], resulting in Taiwan’s fauna and flora having periodic contact with the Asian continent. The topographic complexity and high altitude of the CMR provided opportunities for diversification in Taiwan’s endemic organisms [11,12]
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