DIGITALNA ARHIVA ŠUMARSKOG LISTA
prilagođeno pretraživanje po punom tekstu
|ŠUMARSKI LIST 1-2/2013 str. 31 <-- 31 --> PDF|
corresponds to a ratio of 1:1.09 and indicates larger genetic differentiation among individuals at the higher elevated site than among individuals at the lower elevated site. No significant deviations of observed genotypes from expected genotypes were found at 15 of the total of 16 analysed gene loci when applying χ2 test (α = 0.05). The only exception was detected at the locus 6-Pgdh-B at Vrhovo stand where no statistically significant excess of homozygotes over Hardy-Weinberg expectations was confirmed. The observed frequencies of genotypes in both populations of beech agree with Hardy-Weinberg expectations under random mating at the level of risk α =0.05.
The degree of genetic differentiation between populations was analysed with χ2 tests of homogeneity among allele frequencies for particular gene loci at the level α = 0.05 and α = 0.01. The results have shown significant differences in allelic (genetic) structures between sampled populations of beech at 5 out of 16 analysed gene loci (Table 3). The sampled populations of beech did not share 17 % of their alleles at locus 6-Pgdh-A and 13 % of their alleles at loci Aco-B and Idh-A as well as 30 % of their genotypes at locus 6-Pgdh-A, 24 % of their genotypes at locus Idh-A and 12 % of their genotypes at locus Skdh-A (genotypes values not introduced in Table 3). The mean value of Gregorius (1974) allelic and genotypic genetic distances (d0) amounts to 6.1 % and 11.4 %, respectively, shows that the genetic differences of two local sampled beech populations from different sites on the Gorjanci Mountains are comparatively high.
Two very specific beech forests of Gorjanci Mountains on significantly different forest sites, in different ecological conditions and with different forest-management history were selected. The Vrhovo population was sampled in the hilly area and belongs to site of Hedero-Fagetum. The Kozarje population was sampled in the mountainous zone and belongs to site Lamio orvalae-Fagetum. The results of the genetic study refer to the genotypes of 100 adult trees in two populations at 16 polymorphic co-dominant inherited isoenzyme loci.
The observed genotypes were consistent with the expectations under random mating, and indicated that both sampled populations are randomly mating. At 16 polymorphic enzyme gene loci, 43 allelic variants were found in total, which correspond to 2.69 alleles per locus. Beech from the sampled local stands in Gorjanci Mountains seems to have a similar number of alleles per locus as the overall value for beech in Europe, according to Müller-Starck et al. (1992). This value also corresponds well with A/L = 2.8 obtained for Slovenia (Brus et al. 1999) and was higher than was reported for north-western Italy A/L = 2.12 (Belleti and Lanteri 1996) and Germany A/L = 2.51 (Konnert 1995). The average A/L values observed in the sampled beech populations on the Gorjanci Mountains (2.50 and 2.56) show higher values than was determined for 13 beech populations in Slovenia (Brus et al. 1999) where A/L values varied in range from 2.08 to 2.42 and were close to the highest value obtained in the population of Luknja from Prečna close to Novo Mesto. Beech from Luknja originated from mainly southern-orientated steep limestone walls close to the Palaeolithic site from which beech charcoal from the late Pleistocene has been excavated (Osole 1990); it may represent a relict population that persisted in a sheltered micro-refugium where it was able to survive the last glaciations (Brus et al. 1999). Therefore it seems that no restriction in genetic multiplicity was determined in beech populations at Gorjanci Mountains.
The populations of European beech at Vrhovo and Kozarje which belong to sites of Hedero-Fagetum in the hilly area and Lamio orvalae-Fagetum in the mountainous zone, respectivetly are autochthonous. The higher altitude stand at Kozarje showed higher genetic diversity than the lower altitude stand at Vrhovo. Differences are evident in the frequencies of some alleles and genotypes, observed heterogosity and particularly in the hypothetical gametic multilocus diversities. The frequency of the allels 6-Pgdh-B1, Aco-B2 and Idh-A2 at the higher elevated Kozarje stand were more than twice as high as of the lower elevated stand. The frequency of the allele 6-Pgdh-A4 was about three times higher in the (lower elevated) Vrhovo stand than in the (higher elevated) Kozarje stand. At locus Skdh-A, allele (A4) was observed only in the Vrhovo stand as a heterozygote genotype Skdh-A34 (12 %). The frequency of the genotype Skdh-A34 significantly changed with altitude. They might be naturally distributed in lower elevated stands but not present in the upper elevated stands and might be a confirmation of the existence of a discontinuity point between these two local populations. Further studies in forests of Gorjanci Mountains should be preformed to prove the hypothesis of the interaction between disruptive natural selection and gene flow in development of among population genetic differentiation.
Our findings confirm findings from comparable studies of beech populations in Germany, related to climatic adaptation with an altitudinal transect from the base of the mountain to its top. In an inventory study on the isozyme genetic variation of beech stands growing at elevations between 350 m and 1250 m a.s.l. in mountain Schauinsland, southwest Germany, allele frequencies of different enzyme systems at gene loci Aco-B, Idh-A, Pgm-A were found to be changed (Löchelt and Franke 1995). Climate adaptation and manmade selection were considered to be causes. A detailed investigation of six autochthonous beech stands growing at elevations between 150 m and 660 m a.s.l. in the same