Format: ORAL

Begoa Quirs-de-la-Pea1,2, Ladislava Patov2, Jindrich Chrtek2, Elika Zvesk1,2, Yann J. K. Bertrand2, Jirina Josefiov2, Shook Ling Low2, Simon V. Corrales2, Barbora Tomeov2, Zuzana Sejfov2, Pavel Zdvork1, Alexander Belyayev2, Patrik Mrz1

1 Charles University, Prague, Czech Republic 2 Institute of Botany of the Czech Academy of Sciences, Pruhonice, Czech Republic

Hieracium s.str. (Asteraceae) is a highly diverse genus that occurs in a wide range of environments, from lowlands to the alpine zone. It is known for its notorious taxonomic complexity, caused by widespread past interspecific hybridisation. This process has been closely linked to polyploidisation and apomixis, which has ensured the persistence of otherwise sterile hybrids. As a result, Hieracium is the largest apomictic-sexual genus among angiosperms, whose diversity is dominated by apomictic polyploid species. However, very little is known about the evolutionary and biogeographical history of these apomictic polyploids. We aim to decipher the evolutionary history of the alpine apomictic species H. halleri, which probably arose from hybridisation between H. alpinum and H. intybaceum. We also ask if H. halleri originated only once or if it is of recurrent hybrid origin. To achieve these aims, we combined cytogenetic (FISH and GISH), flow cytometric (assessment of mode of reproduction), and molecular (RADSeq, cpDNA) approaches. This multidisciplinary approach is applied to plants collected across the range of the species, which shows a large disjunction between the Alps and the Western Carpathians. We found that despite strictly apomictic mode of reproduction, H. halleri is cytogenetically variable taxon, both in chromosome number (prevailing are triploids, tetraploids are very rare) and karyotype pattern (variation in number and positions of 5S rDNA, 45S rDNA and HintCL-82 repetitive DNA clusters, and unbalanced translocations). Prevailing triploid H. halleri cytotype contains two genomes of H. alpinum and one genome of H. intybaceum, the pattern explaining the much closer morphological affinity of H. halleri to H. alpinum. Furthermore, cytogenetic and phylogenomic data indicate multiple origin of H. halleri. To conclude, multiple hybridisation events, post-hybridisation chromosomal rearrangements, and migration to the Western Carpathians have shaped molecular and biogeographic histories of this species.