Population dynamics linked to glacial cycles in Cercis chuniana F.P.
Metcalf (Fabaceae) endemic to the montane regions of southern China
The mountains of southern China are an excellent system for
investigating the processes driving the geographic distribution of
biodiversity and radiation of plant populations in response to
Pleistocene climate fluctuations. How the key mountain ranges in
southern China have affected the evolution of narrowly distributed
species is less studied than more widespread species. Here we focused on
Cercis chuniana, a woody species endemic to the southern mountain ranges
in subtropical China, to elucidate its population dynamics. We used
genotyping by sequencing (GBS) to investigate the spatial pattern of
genetic variation among 11 populations. Bayesian time estimation
revealed that population divergence occurred in the middle Pleistocene,
when populations in the Nanling Mts. separated from those to the east.
Geographical isolation was detected between the populations located in
adjacent mountain ranges, thought to function as geographical barriers
due to their complex physiography. As inferred by ecological niche
modeling and coalescent simulations, secondary contact occurred during
the warm Lushan-Tali interglacial period in China, with intensified East
Asia summer monsoon and continuous habitat available for occupation.
Complex physiography plus long-term stable ecological conditions across
glacial cycles facilitated the demographic expansion in the Nanling
Mts., from which contemporary migration began. Our work shows that
population genomic approaches are effective in detecting the population
dynamics of narrowly distributed species. This study advances our
understanding how glacial cycles have affected the evolutionary history
of plant species in southern China montane ecosystems.