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Evolutionary aspects in Hieracium subgenus Pilosella
| Content Provider | Semantic Scholar |
|---|---|
| Author | Fehrer, Judith Krahulcová, Anna Krahulec, František Rosenbaumová, Radka Bräutigam, Siegfried |
| Copyright Year | 2007 |
| Abstract | The hawkweed Hieracium subgenus Pilosella (Cichoriae, Asteraceae) is known for its notoriously complicated taxonomic structure due to ongoing reticulate evolution, combined with a facultative apomictic mode of reproduction and allopolyploidy. Recently, molecular approaches at the clone, population and species level have begun to shed some light on these processes. Gene flow across ploidy levels is common, and parental species of hybrid taxa often include apomicts, even as seed parents. Sexual taxa (diploid or polyploid) usually show high genetic variability. Apomicts vary from near clonality across large geographic distances to multiple origins on a small scale. Selection plays an important role in the establishment and fixation of particular cytotypes/genotypes in the field. A broad range of reproductive strategies and frequent hybridizations, combined with good colonization properties under low-competition conditions in their native Eurasian environment, provide an enormous evolutionary potential, which is also reflected by the group’s strong invasive behavior on other continents. Phylogenetic analyses reveal that Pilosella chloroplast haplotypes form two major groups with no correlation to morphology and taxonomic grouping whereas nuclear DNA sequences reflect species relationships. Incongruence between molecular markers implies two ancient hybridization events predating most of the speciation observed in the subtribe Hieraciinae: one between the Hieracium/Chionoracium subgenera ancestor and partly differentiated Pilosella, and a subsequent event between this introgressed Pilosella lineage and the closely related Andryala genus ancestor. Distribution areas and numbers of Pilosella species belonging to one or the other haplotype group as well as the extinction of intermediate haplotypes suggest their differentiation in different glacial refuges. The introgressed Pilosella lineage gave rise to the majority of recent species which show an increased ecological amplitude. Secondary contact generated a large geographic overlap of haplotype groups with no apparent reproductive isolation between species. Phylogenetic, developmental genetic, biogeographic, and mechanistic aspects of the origin of polyploidy and apomixis in Pilosella are discussed, and guidelines for dealing with natural populations of apomictic groups are suggested. A comprehensive list of adventive Pilosella species, an updated map of their native range, and a preliminary map of the distribution of Andryala are provided. |
| File Format | PDF HTM / HTML |
| Alternate Webpage(s) | http://www.ibot.cas.cz/hieracium/studygroup/pdfs/Fehrer_et_al2007b.pdf |
| Language | English |
| Access Restriction | Open |
| Content Type | Text |
| Resource Type | Article |
