Chromosome Number Evolution in Cirsium Mill. and Carddus L. (Asteraceae)

Chromosome numbers and karyotypes in flowering plants have been considered to be prominent features in taxonomic and evolutionary context. Despite the increasing numbers of cytological studies in Asteraceae, karyotype analysis of Cirsium Mill. and Carddus L. in Korean population have not been performed carefully. In this study, the chromosome numbers and karyotype analysis of all eight species of the genus Cirsium Mill. and one species of Carddus L. were analyzed. While the chromosome number in Carduus crispus L. was diploid (2n = 2x = 18 or 18+2Bs) with x = 9 as the base chromosome number, all seven species of Cirsium were diploid with x = 17 except for Cirsium lineare (Thunb.) Sch. Bip. (x = 14). The chromosome number in C. pendulum Fisch. ex DC. presented 2n = 2x = 34 from two populations and C. lineare exhibited 2n = 2x = 28 from one population. Aneuploidy was occasionally found in C. japonicum Fisch. ex DC. var. spinossinum Kitam. (2n = 2x = 34, 35, 36), C. rhinoceros (H. $L{\acute{e}}v.$ & Vaniot) Nakai (2n = 2x = 32, 34), C. setidens (Dunn) Nakai (2n = 2x = 30, 31, 32) and C. vlassovianum Fisch. ex DC. (2n = 2x = 31, 32). While Cirsium japonicum Fisch. ex DC. var. japonicum possessed several B-chromosomes (2n = 2x = 34, 35, 36), polyploidy was only encountered in Cirsium nipponicum (Maxim.) Makino. (2n = 4x = 68) from two populations in Ulleung Island. The present cytological data might be contributed to the taxonomic and evolutionary studies in the genus Cirsium.