Eighteen European beech (Fagus sylvatica L.) populations, twelve of which are relatively undamaged and six severely damaged, were analyzed. Six populations were young; three of them polluted and three unpolluted. The following twelve isozyme loci were used: GOT-8, IDH-A, LAP-A, MDH-A, MDH-B, MDH-C, MNR, PX-A, PX-6, PGM, PGI-B and SKDH. Significant differences of allelic frequencies between the groups of polluted and unpolluted populations on loci LAP-A and IDH-A were determined. The genetic distances between the old population and its progeny are, in ali cases, higher on polluted sites than on unpolluted ones. It is very likely that pollution has caused a substantial change in allelic frequencies, which is also indicated by greater genetic distances between polluted and unpolluted populations as well as between polluted populations only. There are some indications that selection against some alleles is present, but this was not unambiguously confirmed in the study.
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