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Using demographic model selection to untangle allopatric divergence and diversification mechanisms in the Rheum palmatum complex in the Eastern Asiatic Region

Feng, Li1; Ruhsam, Markus2; Wang, Yi-Han3; Li, Zhong-Hu4; Wang, Xu-Mei1

Published Apr 22, 2020; Updated Dec 26, 2020 on Dryad. https://doi.org/10.5061/dryad.jh9w0vt7s

Data files

Apr 22, 2020 version files 11.06 MB

Abstract

Allopatric divergence is often initiated by geological uplift and restriction to sky-islands, climate oscillations, or river capture. However, it can be difficult to establish which mechanism was the most likely to generate the current phylogeographic structure of a species. Recently, genomic data in conjunction with a model testing framework have been applied to address this issue in animals. To test whether such an approach is also likely to be successful in plants we used population genomic data of the Rheum palmatum complex from the Eastern Asiatic Region, in conjunction with biogeographical reconstruction and demographic model selection to identify the potential mechanism(s) which have led to the current level of divergence. Our results indicate that the R. palmatum complex originated in the central Hengduan Mts. and possibly in regions further to the east, and then dispersed westward and eastward resulting in genetically distinct lineages. Populations are likely to have diverged in refugia during climate oscillations followed by subsequent expansion and secondary contact. However, model simulations within the western lineage of the R. palmatum complex cannot reject a restriction to sky-islands as a possible mechanism of diversification due to the genetically ambiguous position of one population. This highlights that genetically mixed populations might introduce ambiguity regarding the best diversification model in some cases. Although it might be possible to resolve this ambiguity using other data, sometimes this could prove to be difficult in complex biogeographic areas.