###### Abstract  
The evolution of the karyotype and genome size was examined in species of _Crepis_ sensu into. The phylogenetic relationships, inferred from the plastid and nrITS DNA sequences, were used as a framework to infer the patterns of karyotype evolution. Five different base chromosome numbers (\(x\) = 3, 4, 5, 6, and 11) were observed. A phylogenetic analysis of the evolution of the chromosome numbers allowed the inference of \(x\) = 6 as the ancestral state and the descending dysploidy as the major direction of the chromosome base number evolution. The derived base chromosome numbers (\(x\) = 5, 4, and 3) were found to have originated independently and recurrently in the different lineages of the genus. A few independent events of increases in karyotype asymmetry were inferred to have accompanied the karyotype evolution in _Crepis_. The genome sizes of 33 _Crepis_ species differed seven-fold and the ancestral genome size was reconstructed to be 1C = 3.44 pg. Both decreases and increases in the genome size were inferred to have occurred within and between the lineages. The data suggest that, in addition to dysploidy, the amplification/elimination of various repetitive DNAs was likely involved in the genome and taxa differentiation in the genus. chromosome number; karyotype formula; flow cytometry; genome size; phylogenetic analysis 2021 12 1436 1  
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karyomorphotypes based on the number and morphology of the chromosomes and the symmetry/asymmetry of the karyotypes [15]. The first comprehensive sectional classification of _Crepis_ was largely based on a combination of chromosomal and morphological characters of the species [11; 15; 16]. Thus, the genus _Crepis_ has been considered to be the first model plant group in which chromosomal evolution plays an important role in speciation (e.g., [13; 17; 18; 19]). The morphological, cytological and physiological evidence suggested that a decrease in the base chromosome numbers and a shortening of the life cycle accompanied the evolution of the genus [20]. Decreases in the chromosome numbers from an ancestral \(2n=12\) to the derived \(2n=10\), \(8\), and \(6\) have been suggested to have occurred mostly via the reciprocal translocations between non-homologous chromosomes [20]. In the diversification and speciation of the genus _Crepis_, the decreases in the base chromosome numbers and increases in karyotype asymmetry were suggested to be the main direction of the evolution of the karyotype [13; 20]. Symmetrical karyotypes composed of mostly metacentric and submetacentric chromosomes of similar sizes were usually considered to be presiomorphic. Asymmetrical karyotypes, considered to be apomorphic, are composed of highly variable in size chromosomes. Most of their chromosomes have terminally or subterminally localised centromeres [13; 21]. This suggested that the most derived _Crepis_ species possessed \(x=3\) chromosomes, asymmetrical karyotypes that were primarily annuals [13; 20]. Molecular phylogenetic studies of the genus _Crepis_ sensu lato (s.l.) tested [PERSON]'s hypothesis in a phylogenetic framework [22] and proposed a new classification of this genus. Three evolutionary lineages were distinguished based on the analyses of 75 taxa: (i) species with a chromosome base number \(x=7\), corresponding to [PERSON]'s section _Ixeridopsis_ and now placed in genus _Askellia_; (ii) [PERSON]'s sections _Intybellia_, _Lagoseris_, _Phueacasium_, _Microcephalum_, and _Pterotheca_, as well as two other genera, _Lapsana_ and _Rluagadiolus_, now included in the _Lagoseris_ evolutionary lineage; and (iii) _Crepis_ sensu stricto (_Crepis_ s.s.), which comprised the remaining analysed _Crepis_ species [22; 23]. The new sections were highly heterogeneous compared to [PERSON]'s sections, also concerning base chromosome numbers, suggesting that the infrageneric classification of [PERSON] did not represent natural groups [20; 22; 23].