Data from: Multiple glacial refugia for cool-temperate deciduous trees in northern East Asia: the Mongolian oak as a case study

In East Asia, temperate forests are predicted to have retracted southward
to c. 30° N during the last glacial maximum (LGM) based on fossil pollen
data, whereas phylogeographic studies have often suggested glacial in situ
survival of cool-temperate deciduous trees in their modern northern
ranges. Here we report a study of the genetic diversity and structure of
29 natural Mongolian oak (Quercus mongolica) populations using 19 nuclear
simple sequence repeat (nSSR) loci and four chloroplast DNA fragments.
Bayesian clustering analysis with nSSRs revealed five groups, which were
inferred by approximate Bayesian computation (ABC) to have diverged in
multiple refugia through multiple glacial–interglacial cycles. Analysis of
chloroplast DNA variation revealed four lineages that were largely but
incompletely geographically disjunct. Ecological niche modelling (ENMs)
indicated a southward range shift of the oak's distribution at the
LGM, although high suitability scores were also evident in the Changbai
Mts. (Northeast China), the Korean Peninsula, areas surrounding the Bohai
Sea, and along the coast of the Russian Far East. In addition, endemic
chloroplast DNA haplotypes and nuclear lineages occurred in high-latitude
northern areas where the ENM predicted no suitable habitat. The combined
evidence from nuclear and chloroplast DNA, and the results of the ENM
clearly demonstrate that multiple northern refugia, including cryptic
ones, were maintained across the current distributional range of the
Mongolian oak during the LGM or earlier glacial periods. Though spatially
limited, postglacial expansions from these refugia have led to a pattern
of decreased genetic diversity with increasing latitude.