Chromosome Numbers in the Genera Cousinia, Olgaea and Syreitschikovia (Compositae)

The scarce karyological data available for both the Arctium-Cousinia complex and the Onopordum group has led us to provide more data essential to understand the karyological evolution of these taxa. Chromosome counts were made on somatic metaphases using the squash technique. We report 20 chromosome number records for the genus Cousinia s. lat. from the area of Near East and Central Asia. Thirteen of them are first chromosome counts for the studied species, and the remaining seven records provide confirmation of scarce or uncertain previous data. We also present the first chromosome counts for three of the 13 sections of this genus. Our records for Arctioid species show karyological uniformity with 2n=36. In the Cousinioid group, 13 records agree with the three major numbers of its characteristic dysploidy series 2n=22, 24 and 26. We report first chromosome counts for the genera Olgaea and Syreitschikovia from Kazakhstan, being 2n=26 and 24, respectively. Our results confirm a hypothesis that the Arctioid and Cousinioid clades, although forming a monophyletic group, have followed different evolutionary paths. In the Onopordum group, our results confirm the existence of two lineages; the colonizing biennial taxa are characterized by n = 17, while the perennial genera have n = 12, 13. The evidence for recent polyploidization is absent in both the Arctium-Cousinia complex and the Onopordum group.