| Abstrakt: |
Abstract: a1_Polyploidy, aneuploidy and change in DNA content of monoploid genomes or chromosomes are the principal causes of the variation in genome size. We studied these phenomena in central-European populations of the Valeriana officinalis complex in order to identify mechanisms or forces driving its evolution. The complex comprises di-, tetra- and octoploid morphologically defined so-called taxonomic "types". Within the study area there are also intermediate “transitional types” the existence of which hampers the application of traditional taxonomic concepts. We thus chose AFLP genotyping and admixture analyses to identify the genetic structuring of the material studied. Di- (2x), tetra- (4x) and octoploidy (8x) were confirmed as major ploidy levels. Major genetic clusters roughly corresponded to these ploidy levels (for K = 2: 2x- and 8x-clusters, for K = 4 with nearly identical probability: 2x-, 4x-, 8x- and unspecific clusters were identified), which further more significantly differed from each other in monoploid absolute genome size (mean 1Cx for 2x = 1.48 pg, 4x 1.29 pg, 8x 1.10 pg). Several individuals of all ploidy levels were admixed, particularly tetraploids. Relative genome size (the sample: standard DAPI fluorescence) was positively correlated with the proportion of the diploid genetic cluster shared by the tetraploids, indicating that hybridization caused the variation in genome size. This result is in accordance with the significant negative correlation of the genome size of tetraploids with their geographic distance to the diploids. However, remarkable intra-ploidy variation in relative genome size was recorded for all ploidy levels (1.14-fold in diploids, 1.28-fold in tetraploids, 1.19-fold in octoploids). We identified aneuploidy as an additional source of variation in genome size in the di- and tetraploids. |
