| dc.description.abstracteng | In beech stands (Fagus sylvatica) it is observed, that beech trees with specific trunk morphology, such as forked stems, often occur in groups. At the same time, in naturral regenerated beech stands distinct family structures can be assumed due to a limited pollen and especially seed dispersal. Aim of this work is the investigation of spatial distributions of such family structures. Based on genetic investigations of morphologically differentiated individuals and their natural regeneration in three beech stands in Germany, a possible relation between the variability of the trunk morphology and the genetic variation could be detected. The outcrossing rate estimated by using isoenzyme gene markers was relatively high for all the investigated individuals, as expected. The study of nine enzymatic gene loci GOT-B, IDH-A, MDH-B, MDH-C, PGI-B, PGM-A, LAP-A, 6PGDH-A and MNR-A did not show any clear genetic differentiation between the forked and monopodial groups of trees, that means there was no indication about enzymatic genotypes, which strongly promote the formation of forked stems. The application of geostatistical methods for the study of the spatial distribution of the genetic variation enables the identification of spatial structures. The autocorrelation analysis according to MORAN (1950) showed a low correlation between the spatial and genetic distances in each of the studied beech stands. The results of the present study pointed out that in a beech stand both the family structures and the action of a microenvironmental selection should be taken into consideration for the interpretation of the spatial distribution of genetic information. The investigation of the spatial distribution of genetic variants in beech populations by using the grouping index and the sum of the allele frequencies for increasing distances, especially regarding rare alleles, provides further information for interpretation and takes into consideration further aspects of spatial structuring. The results of this analysis were in accordance with those achieved with the interpolation method. All geostatistic methods applied in the present study confirmed spatial genetic autocorrelation limited in small areas, possibly due to the restricted pollen and especially seed dispersal. It has been showed that the size of these spatial genetic structures can differ between beech stands, depending on factors like stand density and structure, as well as on the effect of a microenvironmental conditions or the influence of human activities. In beech stands with natural regeneration, and consequently various age classes, the diameter of areas of pronounced autocorrelation was estimated to be around 20 to 30 m, increasing with the increasing age of the stand. The molecular markers offer new possibilities for the investigation of phylogenetic relationships and kinship, as well as of the mating system and gene flow within and between populations. For the study of phylogenetic relations and ancestry reconstruction in the female lineages, uniparental inherited markers, such as cpDNA or mtDNA markers, would be the most appropriate. The mating system and gene flow could be investigated with a combination of uniparental and biparental inherited markers, like the nucleus microsatellites. Universal cpDNA markers were already applied for the study of beech populations in Europe and a high genetic differentiation between populations has been detected (DEMESURE et al., 1996). Furthermore, the RFLP analysis of cpDNA from populations in Rheinland-Pfalz in Germany showed variation within a population (VORNAM and HERZOG, 1996), while the PCR-RFLP analysis showed neither in the study of DEMESURE et al. (1996) nor in the present study any variation within a beech population. The development of homologe primers in beech would be of a great importance, because of methodological problems during the PCR reaction by using the universal cpDNA primers. The mitochondrial DNA markers are also very important for the investigation of the gene flow by seeds. The mtDNA molecules are often more variable than the highly conserved cpDNA molecules. Therefore it is expected, that such mtDNA markers are very informativ for phylogenetic analyses in the microevolutionary level (AVISE et al., 1987). The mtDNA markers investigated in the present study were not variable, an indication for highly conserved mtDNA molecules in European beech. Consequently, the maternal inherited markers used in the present study are not appropriate for the identification of the maternal ancestor in family structures in beech stands, since for such investigations high variability of these markers is required. The microsatellites (simple-sequence repeats or SSR) are highly repeated, short DNA sequencies dispersed throughout the genome and the plastids. The repeated unit of such SSR loci is five or fewer bases in length. Microsatellites are very important markers for population genetic studies, mainly because of their high variability. SSR primer developed from the genome of Quercus petraea were tested also on other species of the Fagaceae family.These (GA)n sequencies were not variable in beech. (STEINKELLNER et al., 1997). Microsatellite primers developed from Fagus crenata (TANAKA et al., 1999) were tested in the present study for Fagus sylvatica. These microsatellite regions seem to be very variable in the European beech. However, an inheritance analysis is required for the interpretation of the band patterns and the use of them as genetic markers. The identification of spatial structures of the genetic variation based on the investigation of enzyme gene markers and additional molecular markers, by means of geostatistical methods would be of major practical importance. Such structures could provide information about the possible origin and development of a stand, as well as suggestions about the strategy of collection of seed material, preferably originating from different families. Moreover, such kind of studies offers the possibility to investigate associations between genetic and morphological variation, on the basis of which important information can be achieved about the influence of forest management measures on the genetic structures. Nevertheless, no relation between the spatial distribution of the trees with forked stems and the observed genetic structures were obvious in the present study. | de |