## 4 Discussion
The chromosome numbers of _Crepis_ species analysed in the current study were in accordance with earlier reports [20; 60]. Most of the analysed species were diploids, with only a few polyploids [20]. The tetraploids of _C. vesicaria_ shared the same karyotype structure with its diploid accession, which suggests that they were of autopolyloid origin  
Analyses of chromosome number and genome size evolution in a phylogenetic framework revealed that there was no general trend in their evolution among angiosperms [61; 62; 63]. Both chromosome numbers and genome sizes could change very rapidly during the evolution and diversification of plant genomes [64; 65; 66]. A reduction in genome size was earlier suggested to accompany the evolution of the genus _Crepis_[12; 67], with increases in genome sizes mainly correlated with polyploidisation [20]. However, the present data revealed a bidirectional evolution of genome size in both the _Lagoseris_ and _Crepis_ s.s. evolutionary lineages. The current study revealed that several diploid species have a genome size that is much larger than the ancestral reconstructed states of the lineages they belong to, e.g., _C. panonica_ or _C. pulchra_. This suggested a bidirectional evolution of genome size in at least some of the _Crepis_ lineages. The proliferation of repetitive DNA sequences is considered to be the major cause of the increase in genome size next to polyploidy [7; 24; 68]. The mechanisms of the reduction of genome sizes and DNA removal are less understood, with an unequal homologous recombination or illegitimate recombination proposed to be most important [69; 70]. The information about the genome structure in _Crepis_ is still very limited and only further analyses, especially of repetitive DNA fraction, will allow better insight into the mechanisms of the evolution of genome size in this genus. The ancestral states of the base chromosome number in a common ancestor of _Lagoseris_ and _Crepis_ s.s. was inferred to be \(x=6\), and descending disploidy was inferred as a main trend in the chromosome number evolution in _Crepis_ (Figure 4). The obtained results are partly in agreement with the hypothesis of [PERSON] [20], who suggested that a decrease in the chromosome base number is the main trend in _Crepis_ evolution. However, the derived base chromosome numbers (\(x=5\), 4, and 3) were found to have evolved independently several times in the evolutionary history of the genus. The chromosome base number of \(x=5\) has evolved at least three times during _Crepis_ evolution. Dysploid change from \(x=5\) to \(x=4\) has occurred twice in _Lagoseris_ and eight times in _Crepis_ s.s. The base chromosome \(x=3\) has evolved twice in _Crepis_ s.s. Nearly half of the descending dysploidy events were recovered for the same branches for which changes in genome sizes were inferred (Figure 5). Some descending dysploidy events were accompanied by a reduction in genome sizes whereas others were accompanied by genome size increases and no common trend was observed. Similar patterns have been reported for _Artemisia_ (Asteraceae; [64]) and other plant genera (e.g., _Genlisea_, Lentibulariaceae; [65]). The chromosome base number was inferred to have increased only twice during the evolution of the analysed species. An allopolyploidisation or a duplication of the chromosome number followed by dysploidy is likely to have given rise to the base chromosome of \(x=11\) present in the American agamic complex. The evolution of this lineage was accompanied by an increase in genome size (Figure S8), supporting the hypothesis of the polyploidy origin of this new base chromosome number of \(x=11\). In contrast, the increase in base chromosome number in the evolutionary lineage of _Lapsana_ (from \(x=6\) to \(x=7\)) was accompanied by the genome size downsizing. The chromEvol analyses inferred that the changes in chromosome number in the _Lapsana_ lineage resulted from demiduplication. For demiduplication, a genome increase instead of decrease would be expected.