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Spatial distribution and genetic variation of a population of Sorbus chamaemespilus (L.) Crantz and putative hybrids between S. chamaemespilus, S. aria and S. aucuparia growing in the nature reserve Skalnä Alpa (central Slovakia) were studied. The analysis of spatial patterns using Ripley's K-function revealed a significant clustering of the adults of both S. chamaemespilus and hybrid taxa at distances up to ~15 m and a strong affinity between both taxonomical groups, indicating similar ecological requirements. Bivariate point-pattern analysis considering cardinal direction showed that juvenile individuals of S. chamaemespilus are clustered around the adults up to the distance of ~2 m, whereas in hybrid taxa with larger and more dense crowns, juveniles are clustered at distances more than ~3 m from the adults. The analysis of genetic variation in a subset of adult shrubs using 4 nuclear microsatellite loci revealed that unlike expected, there was no variation in S. chamaemespilus but several genotypes were found in the group of hybrid taxa. Implications for the reproduction system and conservation of the investigated taxa are discussed.
Pollen viability was tested in two hybrid swarm populations of Pinus mugo and P. sylvestris in northern Slovakia and in control populations of the parental species. It was significantly reduced in hybrid populations, as evidenced by average germination percentages ranging from 49.0% and 61.53% and by pollen tube length averaging 74.54-86.47 µm. The corresponding values in the control populations were 78.38-88.5% and 102.92-152.84 µm, respectively. The frequency of microsporogenesis disturbances at the tetrad and mature pollen stages was higher in hybrid swarms than in the control population of P. sylvestris. Based on in vitro germination data, the amount of sterile pollen was estimated at 40-41% in hybrid swarm populations, 12% in P. sylvestris, and 21% in P. mugo.
The Fagus sylvatica L. species complex in Europe and Western Asia comprises two commonly recognized subspecies, F. sylvatica subsp. sylvatica [= F. sylvatica sensu stricto (s. str.)] and F. sylvatica subsp. orientalis (= F. orientalis), and two putatively hybridogenous or intermediate taxa, “F. moesiaca” and “F. taurica”. The present study aimed to examine the demographic history of this species complex using 12 allelic loci of nine allozymes scored in 279 beech populations in western Eurasia. Three sets of phylogenetic scenarios were tested by approximate Bayesian computation: one dealing with the divergence of subspecies and/or regional populations within the whole taxonomical complex, and two others focusing on the potential hybrid origin of “F. moesiaca” and “F. taurica”. The best-supported scenario within the first set placed the time of divergence of regional populations of F. orientalis in the Early Pleistocene (1.18–1.87 My BP). According to this scenario, the Iranian population was the ancestral lineage, whereas F. sylvatica s. str. was the lineage that diverged most recently. “Fagus taurica” was found to have originated from hybridization between the Caucasian population of F. orientalis and F. sylvatica s. str. at 144 ky BP. In contrast, there was no evidence of a hybrid origin of “F. moesiaca”. The best-supported scenario suggested that the Balkan lineage is a part of F. sylvatica s. str., which diverged early from F. orientalis in Asia Minor (817 ky BP), while both the Italian and Central-European lineages diverged from the Balkan one later, at the beginning of the last (Weichselian) glacial period.
Two provenance experiments with Norway spruce in Slovakia were used to reveal trends in the behaviour of provenances after their transfer. Regressions between the average height and survival of provenances and the differences between the geographic and selected climatic characteristics of the place of origin and provenance plots were significant for most of the characteristics tested. Data from the experiment with Polish and Slovak provenances from 1972 indicated that transfer into warmer regions with a longer vegetation period results in improved height growth and survival, with the exception of survival at initial stages. The experiment from 1964 with a broader altitudinal range of provenance plots, but with unadjusted latest measurements at individual plots available, revealed the best height growth of Slovak Norway spruce provenances after their transfer to sites with the mean annual temperature approximately 1°C higher and with the vegetation period 12 days longer than at places of origin. Transfer into lower altitudes, a warmer climate and a longer vegetation period improved survival. In both experiments, transfer to areas with increased rainfall had a negative effect on growth, which is probably associated with the fact that provenances are not able to exploit additional precipitation for the growth in areas with a colder climate and a shorter vegetation period.
Changes in the genetic variation and spatial genetic structures were modelled in a Norway spruce (Picea abies Karst.) population colonizing abandoned pasture area of 100 hectares at the locality Príslopy, Poľana Mts. (Carpathians, Central Slovakia, 48º38’ N, 19º25’E, approx. 900 m a.s.l.). The development in the past was reconstructed on the basis of a series of historical aerial photographs, reflecting primarily the population growth and the colonization process. The future development was predicted using the individual-tree model SIBYLA developed by Fabrika (2003), whereby it reflects the future density-dependent mortality. No significant changes of the allelic richness or gene diversity were observed during the whole period of modelling (1956 to 2065). Fixation index (reflecting the degree of inbreeding) has steadily increased since the initial stage up to the present, and is predicted to increase further, indicating the accumulation of inbred individuals due to the formation of spatially continuous kin groups. This assumption is supported by the development of spatial genetic structures (non-random distribution of genotypes). The distograms of the number of alleles in common (NAC) showed that spatially proximate individuals share significantly more alleles than expected under random distribution of genotypes. Spatial genetic structures were formed at the very early stage of colonization, have persisted until the present and are predicted to be even enhanced in the future. Isolation by distance due to a limited seed dispersal, strong fertility variation and facilitation of seedling establishment in the vicinity of early colonizers are proposed as explanation. The results indicate that Norway spruce, although being the component of many climax forest communities, is capable under certain circumstances to behave as a very efficient pioneer. The species disperses enough seeds on medium distances to reach suitable sites within open areas and establish as seedlings, whereas a strong seed dispersal at short distances and modification of environment near the early colonizers allow the extension of kin groups and gradual occupation of the whole available space.
The effects of the colonization of an abandoned grassland by forest trees and the associated microenvironmental changes on soil properties and the microbial activity of soil were studied along a 170 m transect established on a former pasture colonized by Norway spruce (Picea abies Karst.) in Central Slovakia. The transect with a 5×5 m grid of sampling points crosses all successional stages from a closed forest to an open grassland, representing 50 years of secondary succession. Changes of basal soil respiration, substrate-induced respiration and soil catalase activity in association with tree density, light and temperature regime were examined, and their relationships with chemical soil properties were documented. Generally, light conditions, tree influence and soil temperatures were highly significantly correlated with the distance from the lower transect edge, but the correlation coefficients were not very high (|r| ranged between 0.37 and 0.70), indicating that the microsite conditions within the transect are strongly heterogeneous. With the advance of colonization, the amount of soil organic matter was found to increase, probably in association with a higher amount and a lower quality of litter. Catalase activity exhibits a linear trend along the transect, which is explained by a lower direct insolation of soils (r = 0.28***) and decreasing temperatures (r = 0.36***) in the upper part. Basal respiration is the lowest in the middle of the transect, where colonizing spruces form a dense closed stand with soil covered by a thick layer of raw litter. Both in the lower part covered by species-rich grassland communities and in the upper part, where forest herb species begin to establish, basal respiration is higher, probably due to higher amounts of easily decomposable plant material. In addition to these transect-wide trends, stationary spatial patterns were observed for most soil variables. Generally, microbial activity rates as well as chemical soil properties exhibited spatial continuity up to the distance of approx. 40 to 60 m.
The height growth dynamics of three interspecific crosses with Greek fir (Abies cephalonica Loud.) acting as mother and a control variant from self-pollination were followed throughout a period of 30 years. The hybrid combination A. cephalonica × A. nordmanniana exhibited enhanced growth relative to the selfed control at stage of 4-year old seedlings already, whereas the hybrid A. cephalonica × A. alba only at stage of 9-year old saplings. At age of 30, the heterotic growth persisted only in the latter, the hybrid A. cephalonica × A.nordmanniana was comparable in height growth parameters with a selfed control. The interspecific cross A. cephalonica × A. numidica was remarkable by its accelerated growth during early stages of the development. At age of 4 years it has surpassed in height growth both A. cephalonica × A. alba and control but has declined profoundly during subsequent stages of its development. A conspicuous feature of the hybrid needle anatomy were abundant resin canals and reduced size of some anatomical traits of its needles. In spite of variable growth potentials, all the three interspecific hybrids are recommended for planting in Slovakia, especially at densely polluted areas where domestic silver fir cannot withstand emission pressure.
Thirty silver fir populations originating from the putative suture zones of the postglacial recolonization (Slovenia, Bosnia and Hercegovina, Ukraine) were studied using a mitochondrial nad5-4 gene marker. The geographical distribution of mtDNA haplotypes in the Ukrainian Carpathians and their northern foothills indicates a very recent meeting of migration streams arriving from the Romanian Carpathians and Central Europe. In the western part of the Balkan Peninsula, two counterparallel migration streams are the most plausible explanation of the pattern observed. The haplotype typical for the Balkan Peninsula predominates along the Adrian coast, whereas the CentralEuropean haplotype is more represented in the inland.
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