Natural regeneration of Fagus sylvatica L. adapts with maturation to warmer and drier microclimatic conditions

Due to its drought sensitivity, the performance and competitiveness of beech as a favoured species of forest management in Central Europe is likely to be negatively affected by the prognosticated climate change, leading to major impacts on the vulnerability of managed forest ecosystems. We studied the genetic differentiation between two populations from a relatively cold and wet northeast (representing the current climate of the majority of beech forests in Central Europe) and a relatively warm and dry southwest facing slope (representing the future climate of an increasing area covered by beech forests in Central Europe) at the same forest site to investigate the adaptation processes in these two populations under different microclimatic conditions. For this purpose, two different techniques, i.e., nuclear microsatellites (neutral) and isozyme markers (adaptive), were applied to adult trees and natural regeneration at both slopes. Although microsatellites are considered to be neutral markers, they have been shown in several studies to give signals of selectively-driven changes. In our study, two of the five microsatellites behaved as “outlier loci”, exhibiting directional selection. Our results show independent of the technique applied that natural regeneration of the southwest slope and the natural regeneration and adult trees of the northeast slope were genetically closer than the adult trees from the southwest slope. Thus, we conclude that natural selection and potential adaptation account for genetic changes and different genetic structures among the two adult populations in this case study.

► We study two adult populations under different microclimatic conditions.
► We compare genetic diversity of the adult populations and their natural regeneration.
► Case study based on isozymes and microsatellite markers.
► We identified two “outlier microsatellite loci”, exhibiting directional selection.
► Natural selection account for different genetic structures of the adult populations.