Interspecific hybridization in the genus Hieracium s. str.: evidence for bidirectional gene flow and spontaneous allopolyploidization
Abstract
Well-documented cases of recent interspecific hybridization in Hieracium s. str. are very rare. We report combined evidence on recent hybridization between two diploid species, H. alpinum and H. transsilvanicum, based on additive patterns of nrDNA polymorphism (ITS), an intermediate position of hybrid plants in PCO analyses based on AFLP phenotypes, and additivity at one allozyme locus.
Two hybrids were diploid while one was surprisingly tetraploid. This is the first record of spontaneous polyploidization following interspecific crossing in the genus.
Allozyme data suggest the origin of this tetraploid via a triploid bridge with subsequent backcrossing to H. alpinum. All H. x krasani hybrids had the H. alpinum cpDNA haplotype while H. transsilvanicum served as a pollen donor.
The hybrids occurred together with abundant H. alpinum plants; paternal H. transsilvanicum was missing. The direction of hybridization might be influenced by the frequency of parental taxa at the locality.