WITHIN-POPULATION GENETIC-STRUCTURE IN QUERCUS-ROBUR L. AND QUERCUS-PETRAEA (MATT.) LIEBL. ASSESSED WITH ISOZYMES AND MICROSATELLITES

The spatial distribution of alleles is described in a forest stand of natural origin of 5 ha comprising 355 mature Quercus petraea and Q. ro bur trees. Each tree was genotyped for six microsatellite loci. Previo us studies on the same population based on isozymes allowed a comparis on of different markers for the detection of spatial genetic structure . Different statistics were used: differentiation measures at differen t spatial scales, and spatial autocorrelation analysis based on Moran' s index I. For microsatellites, differentiation and autocorrelation we re calculated with unordered alleles (identity in state) and with alle les ordered according to their size. Results showed the same tendency of a significant, but low, spatial genetic structure for markers and d ifferent statistics. Some differences could, however, be detected. Fir st, microsatellites interpreted as unordered alleles exhibit stronger spatial structure than isozymes or microsatellite interpreted as order ed alleles. Second, differentiation and autocorrelation values were hi gher in Q. petraea than in Q. robur. These differences were attributed to species differences in gene flow via pollen or seed.