Search

Black poplar (Populus nigra L.) is a keystone species for riparian ecosystems in Europe. We analysed the structure of genetic diversity of 17 populations from 11 river valleys that are part of seven catchment systems (Danube, Ebro, Elbe, Po, Rhine, Rhone, and Usk) in Europe, in relation to geography and river management. In total, 1069 trees were genotyped using AFLP and microsatellite markers. The trees had an observed heterozygosity of 0.74 (range 0.59-0.82 across microsatellite loci). The majority (72.6-90.8%, depending on the marker system) of the genetic variation was present within populations. Most pairs of populations along a river were relatively similar (pairwise Fst 0.042-0.135 based on AFLP, 0.002-0.037 based on microsatellites). Overall population differentiation among rivers was considerable (Fst among populations was 0.268 based on AFLP, and 0.081 based on microsatellites). An analysis using the program Structure indicated that all populations recruited plants from several clusters. Geographically close populations tended to draw from the same Structure clusters, including populations from adjacent catchments. The Danube and Inn populations in Austria were genetically more similar to the Vltava population (Elbe catchment) in Czech Republic than the geographically more distant populations along the Tisa and Prut rivers of the Danube catchment in Ukraine. This indicates that gene flow and dispersal takes place across fairly large distances and between river catchments. Consistent with this result, a principal coordinate analysis of genetic distances among individual trees based on AFLP bands showed large overlap of populations, although the French and Spanish samples formed distinct clusters, and the samples from the Ticino (Italy) were at an intermediate position. The extent of clonal duplication was highest along regulated rivers, with e.g., 41% clonal duplication along the Rhine in The Netherlands (up to 32 trees for one genet). The Usk contained a m

Black poplar (Populus nigra L.) is a keystone species for riparian ecosystems in Europe. We analysed the structure of genetic diversity of 17 populations from 11 river valleys that are part of seven catchment systems (Danube, Ebro, Elbe, Po, Rhine, Rhone, and Usk) in Europe, in relation to geography and river management. In total, 1069 trees were genotyped using AFLP and microsatellite markers. The trees had an observed heterozygosity of 0.74 (range 0.59-0.82 across microsatellite loci). The majority (72.6-90.8%, depending on the marker system) of the genetic variation was present within populations. Most pairs of populations along a river were relatively similar (pairwise Fst 0.042-0.135 based on AFLP, 0.002-0.037 based on microsatellites). Overall population differentiation among rivers was considerable (Fst among populations was 0.268 based on AFLP, and 0.081 based on microsatellites). An analysis using the program Structure indicated that all populations recruited plants from several clusters. Geographically close populations tended to draw from the same Structure clusters, including populations from adjacent catchments. The Danube and Inn populations in Austria were genetically more similar to the Vltava population (Elbe catchment) in Czech Republic than the geographically more distant populations along the Tisa and Prut rivers of the Danube catchment in Ukraine. This indicates that gene flow and dispersal takes place across fairly large distances and between river catchments. Consistent with this result, a principal coordinate analysis of genetic distances among individual trees based on AFLP bands showed large overlap of populations, although the French and Spanish samples formed distinct clusters, and the samples from the Ticino (Italy) were at an intermediate position. The extent of clonal duplication was highest along regulated rivers, with e.g.;41% clonal duplication along the Rhine in The Netherlands (up to 32 trees for one genet). The Usk contained a ma

Eleven laboratories have collaborated to study chloroplast DNA (cpDNA) variation in black poplar (Populus nigra L.) across Europe in order to improve our understanding of the location of glacial refugia and the subsequent postglacial routes of recolonisation. A common analysis based on the restricted fragments produced by five primer pairs was used to determine the cpDNA haplotype of 637 samples obtained from genebank collections established in nine European countries. Haplotype 2 was particularly common and was found in 46% of the non-hybrid samples. A total of 81 non-hybrid chloroplast variants were detected. Three haplotypes (from four trees believed to originate from Eastern Europe) clustered together and were very different from the rest of the samples. The remaining samples were divided into two groups, one of which had a largely eastern distribution and samples from the other group were mostly located in the west. This, along with the fact that Spain in the southwest and Austria and Italy in the southeast had high diversity, suggest that there were ice age refugia of black poplar in both southwestern (Spain) and southeastern Europe (Italy and/or Balkan). Results also indicate that the Pyrenees formed a significant barrier, since only 7 of the 45 haplotypes in Spain exist elsewhere in Europe. © 2004 Elsevier B.V. All rights reserved.