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Fifteen populations of Pinus mugo subsp. mugo (shrub) and Pinus mugo subsp. uncinata (erect), located in the Alps, were investigated through genetic variation scored at 64 polymorphic RAPD loci. In addition, morphological traits of the female cones were analysed. According to AMOVA most of the genetic variation was found within populations (83.39%), and only 1.25% of it between subspecies. Populations differed in terms of their internal genetic variation, with Nei's gene diversity ranging from 0.227 to 0.397. Morphological data showed differences between subspecies, although none of the populations showed full accordance with expectations. Significant correlation was found between matrices for geographical and morphological distances, while genetic distances were not correlated with any other aspect. The efficacy of morphological and RAPD markers in discriminating between subspecies, and the contribution of the results in relation to the preservation of biodiversity, 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 F IS 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.genetic variation / microsatellite / population differentiation / seed zone designation / Fraxinus excelsior Résumé -Variabilité génétique et différenciation entre populations italiennes de frêne commun (Fraxinus excelsior L.). Le niveau de variation génétique dans l'aire de distribution naturelle du frêne commun (Fraxinus excelsior L.) en Italie a été estimé à l'aide de six marqueurs microsatellite. Des niveaux élevés de diversité allélique ont été détectés. L'hétérozygotie théorique varie de 0,726 à 0,871, avec une moyenne de 0,798, ce qui indique que les populations ont un niveau élevé de variation génétique. Un excès général et significatif de l'homozygotie a été trouvé pour la plupart des loci dans toutes les populations, avec une moyenne globale F IS de 0,284. Des explications possibles pour de telles situations sont proposées. Seulement 4,9 % de toute la diversité est attribuable à la différenciation entre populations. Bien que la divergence entre régions pédo-climatiques explique une petite partie de la variation, il est possible d'observer des regroupements partiels de populations appartenant aux mêmes régions. La contribution de ces résultats à la définition des stratégies les plus appropriées pour rassembler le matériel forestier de reproduction est discutée. diversité génétique / microsatellite / différenciation entre populations / région de provenance / Fraxinus excelsior

Wild service tree [Sorbus torminalis (L.) Crantz] is a forest tree widespread in Europe, characterized by a scattered distribution. Its hermaphroditic flowers are pollinated by insects, and outcrossing is the prominent mating system, also due to the presence of gametophytic self-incompatibility. Genetic diversity and differentiation of 22 populations from northwestern Italy were investigated by means of variation scored at 53 polymorphic RAPD (Random Amplified Polymorphic DNA) loci. Populations differed in genetic variation, with Shannon diversity index ranging from 0.166 to 0.469. According to Analysis of Molecular Variance (AMOVA), most of the genetic variation was found within populations (61.78%) with a significant proportion of variance attributable to genetic differences between regions (23.60%) and between populations (14.62%). Evidence for isolation by distance was found in the set of populations sampled. The effect of habitat fragmentation on genetic variation was also evaluated. The efficacy of RAPD markers in analysing genetic variation, and the contribution of the results in terms of the preservation of biodiversity are discussed.

Silver fir (Abies alba) is a common tree species in the mountainous areas in Europe. A number of natural stands in the hilly regions of northern Europe represent relic populations. The aim of the research was to evaluate the diversity present in Italian populations of the species. Genetic diversity was assessed in 45 silver fir populations covering the species' distribution range in Italy, based on the allelic variation present at seven microsatellite loci (SSRs). A consistent level of intra-population variability was present. Several of the populations displayed signs of ongoing genetic erosion, and evidence for a recent bottleneck in some was identified. Populations from the eastern Alps and the Apennines were more variable than those sampled from the western Alps. About 8% of the overall genetic variance was found between populations, with the remainder representing variation present within the populations. The data suggested that the southern Apennines acted as a refugium during the most recent Ice Age, and that many of the populations from this area have remained isolated over a prolonged period. Smaller and more isolated populations have experienced genetic drift, whereas the larger ones have preserved a high level of diversity. Identification of genetically homogeneous regions could be informative for the management of genetic resources.