Data from: Role of selection and gene flow in population differentiation at the edge vs. interior of the species range differing in climatic conditions

Evaluating the relative importance of neutral and adaptive processes as
determinants of population differentiation across environments is a
central theme of evolutionary biology. We applied the QST-FST comparison
flanked by a direct test for local adaptation to infer the role of
climate-driven selection and gene flow in population differentiation of an
annual grass Avena sterilis in two distinct parts of the species range,
edge and interior, which represent two globally different climates, desert
and Mediterranean. In a multi-year reciprocal transplant experiment the
plants of desert and Mediterranean origin demonstrated home advantage, and
population differentiation in several phenotypic traits related to
reproduction exceeded neutral predictions, as determined by comparisons of
QST values with theoretical FST distributions. Thus variation in these
traits likely resulted from local adaptation to desert and Mediterranean
environments. The two separate common garden experiments conducted with
different experimental design revealed that two population comparisons are
likely to detect population differences in virtually every trait, but many
of these differences reflect effects of local rather than regional
environment. We detected a general reduction in neutral (SSR) genetic
variation but not in adaptive quantitative trait variation in peripheral
desert as compared with Mediterranean core populations. On the other hand,
the molecular data indicated intensive gene flow from the Mediterranean
core towards desert periphery. Although species range position in our
study (edge vs. interior) was confounded with climate (desert vs.
Mediterranean), the results suggest that the gene flow from the species
core does not have negative consequences for either performance of the
peripheral plants or their adaptive potential.