Electrophoretic Analysis of Genetic Variation within and between Populations ofQuercus cerris, Q. pubescens, Q. petraeaandQ. robur(Fagaceae) from Eastern Austria

Allozyme variation at 14 loci was studied electrophoretically in 19 population samples ofQuercus cerris, Q. pubescens, Q. petraea, andQ. robur. Genetic variation, measured as mean heterozygosity, was found to be high within populations but low among populations. A significant deficit of heterozygotes was observed in most of the populations ofQ. pubescens, Q. petraea, andQ. robur. At the species level,Q. cerris(sect.Cerris) appears to be clearly separated from the rest (sect.Quercus).Q. pubescens, Q. petraea, andQ. roburform a cluster of closely‐related species. The degree of genetic differentiation among these species is low, i.e. in the range normally found among con‐specific populations. Nevertheless, allozyme data allow the elaboration of a dendrogram which is in reasonable accordance with the taxonomic classification, but also supports the importance of hybridization and introgression. This is also underlined by the fact that the allelic differentiation at theGot‐2locus corresponds with the phenotypic classification (petraea‐like, hybrids, androbur‐like) in samples from mixed populations.