Mráz, Patrik Chrtek, Jindřich Fehrer, Judith 2011-04-05 Although reticulation has indisputably played an important role in the evolutionary history of the genus <i>Hieracium</i> s. str. (Asteraceae), convincingly documented cases of recent interspecific hybridization are very rare. Here we report combined evidence on recent hybridization between two diploid species, <i>Hieracium alpinum</i> and <i>H</i>. <i>transsilvanicum</i>. The hybrid origin of the plants from the Romanian Eastern Carpathians was supported by additive patterns of nuclear ribosomal DNA polymorphism (ITS), an intermediate position of hybrid plants in principal coordinate analysis based on amplified fragment length polymorphism phenotypes (AFLP), and additivity at one allozyme locus. Flow cytometric analyses and chromosome counting showed that two hybrids were diploid (2n ~ 2x ~ 18) while one was surprisingly tetraploid (2n = 4x = 36). To our knowledge, this is the first record of spontaneous polyploidization following interspecific crossing in the genus. Allozyme data, especially the presence of unbalanced heterozygosity at one locus, suggest the origin of this tetraploid via a triploid bridge with subsequent backcrossing to <i>H. alpinum</i>. According to PCR-RFLP analyses of the <i>trn</i>T-<i>trn</i>L intergenic spacer, all <i>H. </i>×<i>krasani</i> hybrids examined had the <i>H. alpinum</i> haplotype while <i>H. transsilvanicum</i> served as a pollen donor. The hybrids occurred at the locality with abundant <i>H. alpinum</i> plants where paternal <i>H.</i> <i>transsilvanicum</i> was missing. Previously reported instances of interspecific hybridization between the same parental taxa showed an opposite direction of crossing and relative abundance of parental taxa. This suggests that the direction of hybridization might be influenced by the frequency of parental taxa at the locality. application/pdf https://folia.unifr.ch/unifr/documents/302133 https://folia.unifr.ch/documents/302133/files/606_2011_Article_441.pdf eng info:eu-repo/semantics/altIdentifier/doi/10.1007/s00606-011-0441-3 info:eu-repo/semantics/openAccess License undefined Plant Systematics and Evolution. - 2011, vol. 293, p. 237-245 Additive polymorphism AFLP Allozymes Asteraceae Chromosome number nrITS Flow cytometry Hybridization Polyploidization info:eu-repo/classification/udc/57 Interspecific hybridization in the genus Hieracium s. str. : evidence for bidirectional gene flow and spontaneous allopolyploidization http://purl.org/coar/resource_type/c_6501