00510nas a2200157   4500008004100000245010400041210006900145260000900214300001400223490000600237100001400243700001600257700001800273700001800291856004300309       2007                        eng d00aGenetic variation and differentiation within a natural community of five oak species (Quercus spp.)0 aGenetic variation and differentiation within a natural community  c2007  a116 - 1260 v91 aCurtu, A.1 aGailing, O.1 aLeinemann, L.1 aFinkeldey, R.  uhttps://quercus.myspecies.info/node/2102789nas a2200181   4500008004100000245016100041210006900202260000900271300001200280490000700292520215600299100001602455700001802471700001602489700002002505700001802525856006402543       2007                        eng d00aCoincidence of Small-scale Spatial Discontinuities in Leaf Morphology and Nuclear Microsatellite Variation of Quercus petraea and Q. robur in a Mixed Forest0 aCoincidence of Smallscale Spatial Discontinuities in Leaf Morpho  c2007  a713-7220 v993 aBackground and AimsThe taxon complex comprising Quercus petraea and Q. robur shows distinct morphologies and ecological preferences, but mostly low differentiation in various types of molecular markers at a broad spatial range. Local, spatially explicit analyses may reveal patterns induced by microevolutionary processes operating mainly over short distances. However, no attempts have been made to date to explore the potential of spatial analyses combining morphological and genetic data of these oaks. Methods A mixed oak stand was studied to elucidate the small-scale population genetic structure. All adult individuals were classified and putative hybrids were identified using multivariate discrimination analysis of leaf morphological characters. Likewise, all trees were genotyped with five nuclear microsatellites, and a Bayesian assignment method was applied based on maximum likelihood of multilocus genotypes for taxon and putative hybrid classification. Key Results Multivariate analyses of leaf morphological data recognized two groups with few individuals as putative hybrids. These groups were significantly differentiated at the five microsatellites, and genetic taxon assignment coincided well with morphological classification. Furthermore, most putative hybrids were assigned to the taxon found in their spatial neighbourhood. When grouping trees into clusters according to their spatial positions, these clusters were clearly dominated by one taxon. Discontinuities in morphological and genetic distance matrices among these clusters showed high congruence. Conclusions The spatial-genetic analyses and the available literature led to the assumption that reproductive barriers, assortative mating, limited seed dispersal and microsite-induced selection in favour of the locally adapted taxon at the juvenile stage may reinforce taxon-specific spatial aggregation that fosters species separation. Thus, the results tend to support the hypothesis that Q. petraea and Q. robur are distinct taxa which share a recent common ancestry. Occasional hybrids are rarely found in adults owing to selection during establishment of juveniles.1 aGugerli, F.1 aWalser, J.-C.1 aDounavi, K.1 aHolderegger, R.1 aFinkeldey, R.  uhttp://aob.oxfordjournals.org/cgi/content/abstract/99/4/71302668nas a2200157   4500008004100000245010000041210006900141260000900210300000800219490000600227520218000233100001402413700001602427700001802443856004902461       2007                        eng d00aEvidence for hybridization and introgression within a species-rich oak (Quercus spp.) community0 aEvidence for hybridization and introgression within a speciesric  c2007  a2180 v73 aBACKGROUND:Analysis of interspecific gene flow is crucial for the understanding of speciation processes and maintenance of species integrity. Oaks (genus Quercus, Fagaceae) are among the model species for the study of hybridization. Natural co-occurrence of four closely related oak species is a very rare case in the temperate forests of Europe. We used both morphological characters and genetic markers to characterize hybridization in a natural community situated in west-central Romania and which consists of Quercus robur, Q. petraea, Q. pubescens, and Q. frainetto, respectively.RESULTS:On the basis of pubescence and leaf morphological characters  94% of the sampled individuals were assigned to pure species. Only 16 ( 6%) individual trees exhibited intermediate morphologies or a combination of characters of different species. Four chloroplast DNA haplotypes were identified in the study area. The distribution of haplotypes within the white oak complex showed substantial differences among species. However, the most common haplotypes were present in all four species. Furthermore, based on a set of 7 isozyme and 6 microsatellite markers and using a Bayesian admixture analysis without any a priori information on morphology we found that four genetic clusters best fit the data. There was a very good correspondence of each species with one of the inferred genetic clusters. The estimated introgression level varied markedly between pairs of species ranging from 1.7% between Q. robur and Q. frainetto to 16.2% between Q. pubescens and Q. frainetto. Only nine individuals (3.4%) appeared to be first-generation hybrids.CONCLUSION:Our data indicate that natural hybridization has occurred at relatively low rates. The different levels of gene flow among species might be explained by differences in flowering time and spatial position within the stand. In addition, a partial congruence between phenotypically and genetically intermediate individuals was found, suggesting that intermediate appearance does not necessarily mean hybridization. However, it appears that natural hybridization did not seriously affect the species identity in this area of sympatry.1 aCurtu, A.1 aGailing, O.1 aFinkeldey, R.  uhttp://www.biomedcentral.com/1471-2148/7/218