Data from: Multispecies genetic structure and hybridization in the Betula genus across Eurasia

Boreal and cool temperate forests are the major land cover of northern
Eurasia, and information about continental-scale genetic structure and
past demographic history of forest species is important from an
evolutionary perspective and has conservation implications. However,
although many population genetic studies of forest tree species have been
conducted in Europe or Eastern Asia, continental-scale genetic structure
and past demographic history remain poorly known. Here, we focus on the
birch genus Betula, which is commonly distributed in boreal and cool
temperate forests, and examine 129 populations of two tetraploid and four
diploid species collected from Iceland to Japan. All individuals were
genotyped at seven to 18 nuclear simple sequence repeats (nSSRs). Pairwise
math formula among the six species ranged from 0.285 to 0.903, and genetic
differentiation among them was clear. structure analysis suggested that
Betula pubescens is an allotetraploid and one of the parental species was
Betula pendula. In both species pairs of B. pendula and B. plathyphylla,
and B. pubescens and B. ermanii, genetic diversity was highest in central
Siberia. A hybrid zone was detected around Lake Baikal for eastern and
western species pairs regardless of ploidy level. Approximate Bayesian
computation suggested that the divergence of B. pendula and B. platyphylla
occurred around the beginning of the last ice age (36 300 years BP, 95%
CI: 15 330–92 700) and hybridization between them was inferred to have
occurred after the last glacial maximum (1614 years BP, 95% CI: 561–4710),
with B. pendula providing a higher contribution to hybrids.