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In the main distribution area the genetic pattern of silver birch is dominated by two haplotypes: haplotype A located in the western and north-western Europe, and haplotype C in eastern and southeastern Europe, characterized by high levels of neutral genetic variability within populations, and low differentiation among populations. Information about the amount and structure of genetic variation in the southern marginal areas, representing rear populations left during the expansion of this species from southern glacial refugia, are lacking. The general aim of the study was to investigate the existence of the climatic characteristics typical of the environmental niche of the species, jointly to genetic organization, variation and gene flow, in marginal populations on the Italian Apennines and Greek Southern Rhodope and compare them with populations of the southern part of the main distribution range on the Alps and Balkans. Genetic analysis was performed using nuclear microsatellites loci on 311 trees sampled from 14 populations. Environmental analysis was performed on the multivariate analysis of derived climatic variables. The allelic pattern was analyzed to assess genetic diversity, population diversity and differentiation, population structure and gene flow. The geographic and environmental peripherality did not always match, with some Apennine sites at higher elevation enveloped in the environmental niche. In the peripheral populations on the Apennines, we observed a lower genetic diversity and higher differentiation, with evident genetic barriers detected around these sites. These characteristics were not shown in the marginal Greek populations. Unexpectedly, the southern Italian marginal populations showed genetic links with the Greek and central area of the distribution range. The Greek populations also showed evident gene flow with the Alpine and Balkan areas. The disparity of results in these two marginal areas show that it is not the geographic peripherality or even the ecological marginality that may shape the genetic diversity and structure of marginal populations, but primarily their position as part of the continuous range or as disjunct populations. This outcome suggests different considerations on how to manage their gene pools and the role that these rear populations can play in maintaining the biodiversity of this species.

The report describes the geographical and ecological characteristics of the European continental region, which is the area that covers most of Central and Eastern Europe. Forest ecosystems and vegetational aspects, with particular emphasis to forest species growing at the edge of their distribution range, are also considered.

Fritillaria tubiformis subsp. moggridgei Rix. is a rare alpine geophyte with shiny yellow flowers. This plant is sporadically distributed across the southwestern Alps where it is biogeographically close to F. tubiformis var. burnatii Planch. The latter has dark purple flowers and ranges in the majority of the Western and Central Alps. In order to develop appropriate strategies of conservation, a RAPD based analysis was conducted to study the genetic status of these taxa and the distribution of genetic variability of the subspecies by sampling seven populations distributed across the subspecies' range. Four populations of var. burnatii were chosen within this range and included in the genetic analysis. Some 264 individuals were analysed and 201 polymorphic loci were scored. Genetic diversity scored in the subspecies was in line with expectations for endemic species (He = 0.194). F. tubiformis var. burnatii showed lower intraspecific diversity (He = 0.173), notwithstanding a wider range than the subspecies. Most of the total phenotypic variation (about 83%) was allocated within populations, and significant lower proportions between taxa (6.45%) and between populations of the same taxon (10.64%). Moreover, PCoA analysis and Bayesian clustering separated populations into two genetically differentiated groups corresponding with the subspecific taxa. However, three populations ascribed to the subsp. moggridgei repeatedly showed genetic admixture with var. burnatii populations. Our findings suggest that: i) although the different flower colour, the two taxa are genetically very similar and share a consistent part of their gene pool, ii) the majority of genetic variability is allocated within populations rather than among them, iii) a representative amount of genetic diversity can be preserved by sampling from a restricted number of populations. The efficacy of RAPD markers in analysing genetic variation, and the contribution of the results to the preservation of biodiversity of the species, are discussed.

The level of genetic variation throughout the Italian range of common ash (Fraxinus excelsior L.) was estimated using six microsatellite markers. High levels of allelic diversity was detected. The levels of expected heterozygosity for each of the populations ranged from 0.726 to 0.871, with an average of 0.798, and indicated that populations have a high level of genetic variation. A general and significant homozygote excess was found at most loci in all populations, with an overall mean FIS of 0.284. Possible explanations for such situations are discussed. Only 4.9% of the total diversity was attributable to differentiation among populations. Although divergence among pedo-climatic regions explained only a small part of the variance it was possible to observe some partial clustering of populations belonging to the same regions. The contribution of the results in relation to the definition of the most appropriate strategies to collect forest reproductive material is discussed.Variabilit? g?n?tique et diff?renciation entre populations italiennes de fr?ne commun (Fraxinus excelsior L.). Le niveau de variation g?n?tique dans l''aire de distribution naturelle du fr?ne commun (Fraxinus excelsior L.) en Italie a ?t? estim? ? l''aide de six marqueurs microsatellite. Des niveaux ?lev?s de diversit? all?lique ont ?t? d?tect?s. L''h?t?rozygotie th?orique varie de 0,726 ? 0,871, avec une moyenne de 0,798, ce qui indique que les populations ont un niveau ?lev? de variation g?n?tique. Un exc?s g?n?ral et significatif de l''homozygotie a ?t? trouv? pour la plupart des loci dans toutes les populations, avec une moyenne globale FIS de 0,284. Des explications possibles pour de telles situations sont propos?es. Seulement 4,9?% de toute la diversit? est attribuable ? la diff?renciation entre populations. Bien que la divergence entre r?gions p?do-climatiques explique une petite partie de la variation, il est possible d''observer des regroupements partiels de populations appartenant aux m?mes r?gions. La contribution de ces r?sultats ? la d?finition des strat?gies les plus appropri?es pour rassembler le mat?riel forestier de reproduction est discut?e. [ABSTRACT FROM AUTHOR]