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 species is obviously important from an evolutionary perspective but also because of major conservation biology implications. However, although many population genetics studies of forest tree species have been conducted in Europe or Eastern Asia, their continental-scale genetic structure and past demographic history remain poorly known. Here, we focus on the genus Betula, which is commonly distributed in boreal and cool temperate forests, and examined 129 populations of 2 tetraploid and 4 diploid birch species collected from Iceland to Japan. All individuals were genotyped at 7 to 18 nuclear simple sequence repeats (nSSRs). In contrast to chloroplast DNA markers, but in agreement with AFLP markers, genetic differentiation among the six species at nSSR loci was clear. This could be explained by high levels of gene flow within species and high mutation rate of nSSRs. B. pubescens appears to be an allotetraploid of the respective ancestors of the two main diploid species, B. nana and B. pendula. In all species, genetic diversity was highest in Central Siberia. An hybrid zone was detected around Lake Baikal for Eastern and Western species regardless of ploidy level. Approximate Bayesian Computation (ABC) suggested that the divergence of B. pendula and B. platyphylla occurred around the beginning of the last ice age and hybridization between them was inferred to have occurred after the last glacial maximum.