GENETIC-STRUCTURE OF NATURAL STANDS OF FAGUS-SYLVATICA L (BEECH)

The spatial genetic structures of three French natural beech stands we re analysed using polymorphic enzyme loci. Two methods were used: F-st atistics and spatial autocorrelation statistics. Within these stands w here self-fertilization rate is 0, a low heterozygote deficit was obse rved 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 expl ain a significant autocorrelation. Within the two other stands, both d ense, results are similar to those produced by simulations of an isola tion by distance model. The genetic structure seems not to be stable i n space and time which may be due to (i) a limited number of generatio ns; (ii) an effective gene flow less limited than hypothesized; and (i ii) fertility differences or phenological incompatibilities between in dividuals.