Genetic structure of natural stands of Fagus sylvatica L. (beech)

Abstract

The spatial genetic structures of three French natural beech stands were analysed using polymorphic enzyme loci. Two methods were used: F-statistics and spatial autocorrelation statistics. Within these stands where self-fertilization rate is 0, a low heterozygote deficit was observed which may be due to a moderate level of mating between relatives. However, no increase of this deficit was observed from one generation to the next. The spatial genetic structuring was low. Within one open stand composed of several patches, founder events are invoked to explain a significant autocorrelation. Within the two other stands, both dense, results are similar to those produced by simulations of an isolation by distance model. The genetic structure seems not to be stable in space and time which may be due to (i) a limited number of generations; (ii) an effective gene flow less limited than hypothesized; and (iii) fertility differences or phenological incompatibilities between individuals.

Spatial structure of genetic variability in natural stands of Fagus sylvatica L. (beech) in Italy

“…In European beech only a small number of significant autocorrelation values was found in a study of three natural stands in France (Merzeau et a!., 1994). Similar results were obtained in other forest tree species: Picea mariana (Knowles, 1991), Acer saccharum (Perry & Knowles, 1991), Quercus petraea and Q. robur (Bacilieri ci' a!., 1994).…”

“…To our knowledge only one autocorrelation study has been published for beech (Merzeau et al, 1994). In two French populations only five out of 35 and two out of 20 significant SNDs were found.…”

“…We carried out the analysis using both 'allelic' and 'nominal' correlograms following a recent trend in forest tree autocorrelation studies (Merzeau et al, 1994;Bacilieri et al, 1994). In general, for a given population, the two statistics revealed significant results for the same loci although fewer loci showed spatial structuring by 'allelic' than by 'nominal' correlograms.…”

Genetic differentiation in Aspidosperma polyneuron (Apocynaceae) over a short geographic distance as assessed by AFLP markers

“…Low levels of genetic differentiation have been observed between populations of tropical tree species within a short distance of each other (Hamrick and Loveless, 1989;Merzeau et al, 1994;Leonardi and Menozzi, 1996;Takahaski et al, 2000;Mariette et al, 2002). Nonetheless, in A. polyneuron, the genetic variability (Table 1) and genetic differentiation between areas were high (F ST = 0.265; Table 2) for samples within a short distance of each other.…”

“…The use of neutral molecular markers to make inferences regarding adaptive processes is risky, unless natural selection is still in place or there is a strong connection between the selected loci and the neutral markers (Merzeau et al, 1994;Leonardi and Menozzi, 1996;Takahashi et al, 2000;Mariette et al, 2002). The AFLPs revealed a genetic distance (Nei, 1978) of 0.148 between samples of the two areas (Table 1).…”