The spatial distribution of alleles is described in a naturally regenerated, isolated pure beech (Fagus
sylvatica L.) stand consisting of 99 adult trees. After testing nine microsatellite loci originally developed for
F. crenata, each tree was genotyped at four well-scorable microsatellite loci. Specific primers were developed
for one locus of F. sylvatica L. For the characterization of spatial genetic structures, two different statistics
were used. One method is based on the mean genetic distance between trees in different spatial distance
classes, and the other one is Moran’s index I. The results show the same tendency of a strong family
structure in the distance classes up to 30 m in comparison with that expected for a spatially non-systematic
distribution of genotypes. In general, microsatellites are more useful to detect spatial genetic structures than
allozymes. Spatial genetic structures are influenced by unpredictable factors such as wind direction at
anthesis and can therefore vary from year to year. We recommend that seed collections should cover large
areas in order to prevent a preponderance of few families and a reduction of the adaptive potential of the
next generation. Keywords: Fagus sylvatica L., in situ conservation, microsatellites, spatial autocorrelation
