Abstract
BackgroundThe evolutionary origin and historical demography of extant Arcto-Tertiary forest species in East Asia is still poorly understood. Here, we reconstructed the evolutionary and population demographic history of the two extant Euptelea species in China (E. pleiosperma) and Japan (E. polyandra). Chloroplast/nuclear DNA sequences and microsatellite loci were obtained from 36 Euptelea populations to explore molecular structure and diversity in relation to past and present distributions based on ecological niche modelling (ENM). Time-calibrated phylogenetic/phylogeographic inferences and niche-identity tests were used to infer the historical process of lineage formation.ResultsEuptelea pleiosperma diverged from E. polyandra around the Late Miocene and experienced significant ecological differentiation. A near-simultaneous diversification of six phylogroups occurred during the mid-to-late Pliocene, in response to the abrupt uplift of the eastern Tibetan Plateau and an increasingly cooler and drier climate. Populations of E. pleiosperma seem to have been mostly stationary through the last glacial cycles, while those of E. polyandra reflect more recent climate-induced cycles of range contraction and expansion.ConclusionsOur results illustrate how Late Neogene climatic/tectonic changes promoted speciation and lineage diversification in East Asia’s Tertiary relict flora. They also demonstrate for the first time a greater variation in such species’ responses to glacial cycles in Japan when compared to congeners in China.Electronic supplementary materialThe online version of this article (doi:10.1186/s12862-016-0636-x) contains supplementary material, which is available to authorized users.
Highlights
The evolutionary origin and historical demography of extant Arcto-Tertiary forest species in East Asia is still poorly understood
We propose that our dates are still broadly consistent with the mid-Pliocene abrupt uplift of the eastern Tibetan Plateau and adjacent southwest China (c. 3.4 million of years ago (Ma)) [102], and the intensification of Northern Hemisphere Glaciation (3.2–2.5 Ma) [103]
Relative demographic stability of E. pleiosperma in China In contrast with the profound influence of Quaternary climatic fluctuations on the range dynamics of both Cercidiphyllum japonicum [3] and Sargentodoxa cuneata [104] in China, our results suggest a rather limited effect of such climate change on the demographic history and Last Glacial Maximum (LGM) distribution of E. pleiosperma in this region
Summary
The evolutionary origin and historical demography of extant Arcto-Tertiary forest species in East Asia is still poorly understood. The modern patterns of endemism and disjunction of these relicts (e.g. between China and Japan) provide only limited insight into how past changes in climate, tectonics, and/or sea-level influenced their range dynamics and population/species divergence [7,8,9,10]. Recent molecular phylogeographic studies suggest that most Arcto-Tertiary relicts endemic to China have been little affected by Quaternary glacialinterglacial alternation [4, 11, 12]. In those instances, species likely tracked their climatic niche boundaries locally through altitudinal migration in a topographically complex landscape [13,14,15]. The Chinese-Japanese disjunct Cercidiphyllum japonicum responded to Quaternary climate change through
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