Data from: Causes and consequences of large clonal assemblies in a poplar hybrid zone

Asexual reproduction is a common and fundamental mode of reproduction in
plants. Although persistence in adverse conditions underlies most known
cases of clonal dominance, proximal genetic drivers remain unclear, in
particular for populations dominated by a few large clones. In this study,
we studied a clonal population of the riparian tree Populus alba in the
Douro river basin (northwestern Iberian Peninsula) where it hybridizes
with Populus tremula, a species that grows in highly contrasted ecological
conditions. We used 73 nuclear microsatellites to test whether genomic
background (species ancestry) is a relevant cause of clonal success, and
to assess the evolutionary consequences of clonal dominance by a few
genets. Additional genotyping-by-sequencing data were produced to estimate
the age of the largest clones. We found that a few ancient (over a few
thousand years old) and widespread genets dominate the population, both in
terms of clone size and number of sexual offspring produced.
Interestingly, large clones possessed two genomic regions introgressed
from P. tremula, which may have favoured their spread under stressful
environmental conditions. At the population level, the spread of large
genets was accompanied by an overall ancient (>0.1 Myr) but soft
decline of effective population size. Despite this decrease, and the high
clonality and dominance of sexual reproduction by large clones, the Douro
hybrid zone still displays considerable genetic diversity and low
inbreeding. This suggests that even in extreme cases as in the Douro,
asexual and sexual dominance of a few large, geographically extended
individuals does not threaten population survival.