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study of Magri et al. (2006), which analysed large palaeobotanical and genetical data of common beech in Europe. The development of beech forests allowed a possibility that the European beech in the territory of present-day in Slovenia went through a genotypic specialisation that also resulted in locally adapted races or ecotypes. However, in its natural distribution area, very little is known about the patterns of population genetic variation in geographically smaller but heterogeneous areas. The results from beech provenance research in Slovenia represent great phenotypic and phenological differences between Slovenian provenances from various elevations, expositions, climatic conditions (Brinar 1971). Previous studies of genetic structure of beech population in Southeastern Europe have indicated a higher level of genetic diversity in this area (Paule 1995, Gömöry et al. 1999), the predominant ecotypic character of genetic differentiation of populations (Hazler et al. 1997, Gömöry et al. 2007, Ivanković et al. 2008, 2011, Jazbec et al. 2007), and the probability of a glacial refugium along the Slovenia and Croatia (Magri et al. 2006, Brus 2010). In order to look for a possible pattern of beech population genetic variation in geographically smaller and heterogeneous areas, two autochthonous Fagus sylvatica L. populations from different site conditions of Gorjanci Mountains in Slovenia were investigated by means of isoenzyme analyses.
Gorjanci Mountains (syn. Žumberak) are 45–50 km long and 18–22 km wide mountain massive at the south-western edge of the Panonnian plains. The massive with two names (the Gorjanci and Žumberak, on the Slovenian and the Croatian sides, respectively) is characterized by a dynamic relief under influence of two major European geographical and climate units: the Panonnian basin on the north-east and the Dinaric Mountains on the west to south-west (Kutnar et al. 2002). At the bottom of Gorjanci Mountains, beech (Fagus sylvatica L.) forests with mixtures of different tree species, including Quercus petraea (Matt.) Liebl., Carpinus betulus L., Picea abies (L.) H. Karst., Acer pseudoplatanus L., Acer campestre L. and others, cover the major part of the forested area in the transition from the submontane belt to the lowlands. Due to their vicinity to human settlements, they have always sustained heavy anthropogenic impacts. In particular, there are many coppiced forests close to farms. Some of these sites were converted to coniferous monocultures, and many of them were even transformed into agricultural use. In contrast, the human impact is not so pronounced at higher zone of the Gorjanci Mountains, and more or less pure beech stands extend over a larger area. In this area, the share of the coppice and spruce monoculture forests are very low, and forest land-use is prevailing (Marinček and Čarni 2002).
Research plots were selected at different autochthonous beech sites of the Gorjanci Mountains, both belonging to Natura 2000 habitat type of 91K0 Illyrian Fagus sylvatica forests (Kutnar et al. 2011) in the hilly and the mountainous vegetation zone. Two populations of beech at Vrhovo and Kozarje were sampled in "selected" category of forest reproductive material in beech seed stands of provenance Ustraški boršt/Cerov Log at altitude of 273 m (ident. number GSO 5.0222) and provenance of Gorjanci/Kozarje at altitude of 657 m (ident. number GSO 5.0216), respectively (Kraigher et al. 2012). The Vrhovo population belongs to forest of beech and sessile oak with ivy (Hedero-Fagetum Košir 1994 var. geogr. Epimedium alpinum Košir 1979, syn. Querco petraeae-Fagetum Košir 1962). The Kozarje population belongs to the Praedinaric mountain beech forest with dead nettles (Lamio orvalae-Fagetum (Horvat 1938) Borhidi 1963 var. geogr. Dentaria polyphyllos Košir 1962). The distance between sampled populations was 13 km with 384 m in altitude.
Material and Methods
Materijali i metode
Sampling – Uzorkovanje
At the research sites Vrhovo and Kozarje on Gorjanci Mountains, randomly were sampled 100 beech trees for genetic testing over an area of 3.5 ha. In the winter period of 2005/ 2006, we took a branch with dormant buds from each of the sampled trees, which were used for the extraction of enzymes. The buds were preserved until analysis in test tubes at a temperature of –20 °C. The sample was 50 adult trees at each site.
Analysis of isoenzymes – Analiza izoenzima
The genetic variability of the two sampled beech populations was analyzed by means of isoenzyme gene markers using starch electrophoresis as the separation method. Enzyme extraction from dormant buds, electrophoresis conditions and staining, and enzyme visualization was performed according to Konnert et al. (2004). Ten isozyme systems coded by sixteen gene loci were surveyed (Aat syn. Got, Aco, Idh, Mdh, Mnr, Per, Pgi, Pgm, Skdh, 6-Pgdh). The genetic interpretation of banding patterns followed Müller-Starck et al. (2001). The laboratory part of the analyses were performed in the framework of the research tasks of the project Carbon dynamics in natural beech forests (L4-6232) in February 2006.
The results of the isoenzyme analyses were evaluated by the relative allele frequencies, calculated on different gene loci after diploid tree genotypes. Allelic structures in each gene loci were estimated by allelic profiles according to Finkeldey (1993). Genetic multiplicity was measured by the highest