Data from: Relict stands of Central European oaks: unravelling autochthony and genetic structure based on a multi-population study

Central European white oaks expanded rapidly after the last glacial period
and reached their current distribution range during the early
Holocene.  They have been an important resource of timber,
fuelwood and animal feed for humans, who actively promoted their presence
in forests and other landscape types at least since the early historical
times. Besides stands with intensive management, putatively relict
populations of three native oak species can be found on unproductive sites
with restricted accessibility. Here, we apply chloroplast and nuclear
microsatellite markers in order to address the autochthony of relict and
managed stands and compare the spatial distribution of genetic variation
between them. Based on data from more than 150 populations, we demonstrate
that oak autochthony was preserved throughout historical times which is
likely the result of traditional silvicultural treatment. This is
supported by the fact that the spatial pattern of chloroplast haplotype
distribution still reflects the post-glacial recolonization in both relict
and old managed stands. We observed significant admixture of haplotypes
only in stands established after the Second World War, which is
attributable to the transfer of reproductive material used for
afforestation. In terms of nuclear genetic variation, we observed marked
differences among species. Quercus pubescens exhibited a pronounced
genetic structure. Genetic drift and limited gene flow among its small and
isolated populations in our study area might have contributed to this
pattern. Varying extent of genetic introgression with other sympatric oak
species could offer an additional explanation. On the contrary, the gene
pools of Q. petraea and Q. robur are highly homogenous, displaying only
weak isolation-by-distance. We found no significant differences of genetic
diversity and differentiation between relict and managed stands. This
suggests that seed transfer mostly occurred within our study area, even in
those stands established in post-war times, verifying previous findings
that point out limited human interference. We recommend consideration of
population genetic structure for gene conservation, with a finer
resolution of gene conservation units needed for Q. pubescens due to its
spatial genetic structure. Both relict and old managed stands,
species-pure or mixed, are suitable for conservation, as they host
autochthonous gene pools. Coppice-with-standard management could
contribute to preservation of autochthony. In the face of climate change,
it is also important to maintain the evolutionary potential of the stands,
by facilitating generative reproduction and allowing for hybridization in
mixed stands.