Genetic Insights into Ecological Succession from Oak- (Quercus robur L.) to Beech- (Fagus sylvatica L.) Dominated Forest Stands

Abstract

Genetic diversity is often considered a major determinant of long term population persistence and its potential to adapt to variable environmental conditions. The ability of populations to maintain their genetic diversity across generations seems to be a major prerequisite for their sustainability, which is particularly important for keystone forest tree species. However, little is known about genetic consequences of demographic alterations occurring during natural processes of ecological succession involving changes in the species composition. Using microsatellites, we investigated genetic diversity of adult and offspring generations in beech (Fagus sylvatica L.) and oak (Quercus robur L.) populations coexisting in a naturally established old-growth forest stand, showing some symptoms of ongoing ecological succession from oak-to beech-dominated forest. In general, adult generations of both species exhibited high levels of genetic diversity (0.657 for beech; 0.821 for oak), which, however, depended on the sets of selected genetic markers. Nevertheless, several symptoms such as differences in genetic diversity indices between generations, significant levels of inbreeding (up to 0.029) and low estimates of effective population size (48-80) confirmed the declining status of the oak population. On the other hand, the uniform distribution of genetic diversity indices across generations, low levels of inbreeding (0.004), low genetic differentiation among adults and offspring and, most importantly, large estimates of effective population size (119-716), all supported beech as a successive and successful tree species in the studied forest stand.

Genetic Variation of European Beech Populations and Their Progeny from Northeast Germany to Southwest Switzerland

“…In general, no statistically significant differences of the genetic diversity indices were detected between adult stands and seedlings. This finding is in agreement with other beech studies that compared the genetic diversity across generations [14,25,26]. Large effective population sizes can be expected in forest tree species, which was also indicated by our results that further demonstrated no reduction of effective population sizes in the seedlings compared to the adult populations.…”

“…For instance, Westergren et al [25] analyzed the influence of an irregular shelterwood management system on the genetic structure of natural regeneration in two beech stands in Slovenia. Sandurska et al [26] investigated the genetic diversity of adult beech trees and their seedlings in forest stands, showing indications for ongoing ecological succession from oak to beech-dominated forests. Bilela et al [14] studied the genetic composition of adult trees and seedlings of two populations differing in microclimatic conditions using isozymes and SSRs.…”

Oaks as Beacons of Hope for Threatened Mixed Forests in Central Europe

“…So, both higher seed production and vegetative growth seem possible in temperate oaks during climate change. A comparative analysis of genetic diversity in adult and offspring generations in beech and oak populations coexisting in a naturally established oldgrowth forest stand, revealed that adult generations of both species exhibited high levels of genetic diversity (He: 0.657 for beech; 0.821 for oak; depending on the sets of selected genetic markers) (Sandurska et al, 2017).…”

A Circular Chloroplast Genome of Fagus sylvatica Reveals High Conservation between Two Individuals from Germany and One Individual from Poland and an Alternate Direction of the Small Single-Copy Region

“…in drier regions of Germany [5]. However, succession from oak-to beechdominated forest stands is also observed, in particular in north-eastern beech distribution limits [6]. There are several population genetics studies for European Beech available [7][8][9][10][11][12], and some of them are focused on chloroplast-based genetic diversity [9,[13][14][15][16].…”