Three oaks Microsatellite data

Knowledge of interspecific divergence and population
expansions/contractions of dominant forest trees in response to geological
events and climatic oscillations is of major importance to
understand their evolution and demography. However, the
interspecific patterns of genetic differentiation and spatiotemporal
population dynamics of three deciduous Cerris oak species (Q.
acutissima, Q. variabilis and Q. chenii) that are widely
distributed in China remain poorly understood. In this study, we genotyped
16 nuclear loci in 759 individuals sampled from 44 natural populations of
these three sibling species to
evaluate the plausible demographical scenarios
of the closely related species. We also tested the hypothesis that macro-
and microevolutionary processes of the three species had
been triggered and molded by Miocene–Pliocene geological events
and Quaternary climatic change. The Bayesian cluster analysis
showed that Q. acutissima and Q.
chenii were clustered in the same group, whereas Q. variabilis
formed a different genetic cluster. An approximate
Bayesian computation (ABC) analyses suggested that Q. variabilis
and Q. acutissima diverged from their most common
ancestor around 19.84 Ma, and subsequently Q. chenii diverged from Q.
acutissima at about 9.6 Ma, which was significantly associated
with the episodes of the Qinghai–Tibetan Plateau (QTP). In addition,
ecological niche modeling and population history analysis showed that
these three Cerris oak species repeatedly underwent
considerable ‘expansion–contraction’ during the interglacial and
glacial periods of the Pleistocene, although they have varying degrees of
tolerance for the climatic change. Overall, these findings indicated
geological and climatic changes during the Miocene–Pliocene and
Pleistocene as causes of species divergence and range shifts of
dominant tree species in the subtropical and warm temperature areas in
China.