Kvantitativna genetska varijabilost provenijencija obicne bukve Fagus sylvatoca L.) iz jugoistocne Europe
Since the genetic diversity of European beech (Fagus sylvatica L.) in South-East Europe (particularly for adaptive traits) is not well studied, the purpose of this paper is to determine the amount, pattern and possible causes of its adaptive genetic variability, through analysis of selected quantitative traits in a provenance trial. Research was conducted in a provenance trial in which thirteen provenances were analyzed (Table 1). The heights of all survived plants were measured successively after the first three growing seasons at the trial site, while flushing phenology and winter leaf retention were scored in the second and third year. The preliminary analysis showed that differences between provenances in the average values of height, survival and winter leaf retention were significantly influenced by age differences between provenances (due to different time of collecting seed and initial age of seedlings in the trial Table 1), therefore the averages for the listed properties were corrected for additive age effect. Analysis of variance was conducted in order to determine statistical significance of variance components caused by the effects of provenances. REG and CORR procedures were carried out to analyze the relationships between the investigated traits, as well as between the provenance mean values and climatic variables of their source stands (Table 2). Provenance means of real and age corrected traits are shown in figures 1, 2, 3, 4, 5 and 7. The results indicate high levels of genetic variability for all studied quantitative traits. Statistically significant differences were found between provenances (Table 3), but the real data for height, survival and winter leaf retention were impacted with their age differences. Statistically significant differentiation between provenances for height and survival were lost after the additive age effect correction. Between provenance differences for the analyzed traits were tested by Tukey-Kramers test for a possible geographical pattern of genetic structure. Results indicated geographical structure for the height, survival and winter leaf retention in terms of gradual differences in the east-west direction (see Figures 3, 5 and 7). However, apparently clinal variability was primary influenced by age differences. Thus, existence of the variability cannot be confirmed. Moreover, geographical pattern disappeared after the age corrections for provenance mean heights and survival (see Figures 2 and 4). Regression analysis of the provenance mean values and Ellenbergs climate quotients of their source stands were shown (Figures 8, 9, 10). The aim of this analysis was to determine relationship between genetic variability and climatic variables. Weak and statistically insignificant correlations between height/survival and climate quotients were determined. The same results were obtained using real and age corrected data. These traits were under the strong influence of age differences that have accidentally been associated with the geographic position of provenances (western older than eastern). It was most probably the cause of the obtained geographic structure. On the other hand, the age corrected values of winter leaf retention were significantly correlated with EQs. There was gradual (clinal) differentiation of populations in the westeast direction (the frequency of trees with dead leaves retention gradually decreased from west to east) and declining trend of trees with leaves retention associated with an increasing continentality (Figure 9). It should be mentioned that western provenances were older than eastern ones and the increase of EQs was moderately correlated with geographic position of provenances (EQs of eastern provenances were on average higher than western). For these reasons, differences between provenances in percentage of trees with winter leaf retention are more likely attributable to their age differences, rather than genetic differentiation. Geographical structure of genetic differences between provenances was not shown for flushing phenology. Results indicate an ecotypic (random) pattern of interpopulation differences (Figure 6). There was a statistically significant correlation between provenance mean values and Ellenbergs climate quotients (EQs). Provenances from wetter and cooler habitats (EQ=12-16) were later flushers. With the increase of continentality, provenances showed a trend of earlier flushing. The peak of this trend was observed at the EQ=26, after which the provenances showed a reverse trend, i.e. again flushing later (Figure 10). Despite the fact that differentiation was not detected for traits which were influenced by age differences (height, survival and winter leaf retention), it is more likely that population differentiation in South-East Europe has ecotypic pattern that is shaped by macroclimatic adaptation. This assumption is based on similar studies by other authors (Matyas et al. 2009), but also on our own results for the flushing phenology. It can be recommended that European beech seed zone delineation and use of its forest reproductive material should be done accordingly to ecological besides the geographic criteria.