ELECTROPHORETIC ANALYSIS OF GENETIC-VARIATION WITHIN AND BETWEEN POPULATIONS OF QUERCUS-CERRIS, QUERCUS-PUBESCENS, Q-PETRAEA AND QUERCUS-ROBUR (FAGACEAE) FROM EASTERN AUSTRIA

Allozyme variation at 14 loci was studied electrophoretically in 19 po pulation samples of Quercus cerris, Q. pubescens, Q. petraea, and Q. r obur. Genetic variation, measured as mean heterozygosity, was found to be high within populations but low among populations. A significant d eficit of heterozygotes was observed in most of the populations of Q. pubescens, Q. petraea, and Q. robur. At the species level, Q. cerris ( sect. Cerris) appears to be clearly separated hem the rest (sect. Quer cus). Q. pubescens, Q. petraea, and Q. robur form a cluster of closely -related species. The degree of genetic differentiation among these sp ecies is low, i.e. in the range normally found among con-specific popu lations. Nevertheless, allozyme data allow the elaboration of a dendro gram which is in reasonable accordance with the taxonomic classificati on, but also supports the importance of hybridization and introgressio n. This is also underlined by the fact that the allelic differentiatio n at the Got-2 locus corresponds with the phenotypic classification (p etraea-like, hybrids, and robur-like) in samples from mixed population s.