Chromosome Evolution in Korean Carduus-Cirsium Taxa (Asteraceae)

Abstract

The genus Cirsium is a member of the tribe Cardueae (Asteraceae) and is distributed in the northern hemisphere. The Carduus-Cirsium group has a long history of taxonomic confusion due to its complicated morphological and molecular phylogenetic data. Here, we report the chromosome numbers and karyotypes of nine currently recognized Korean Cirsium species, as well as their closely related taxa, Carduus crispus, to better understand the chromosomal evolution using classic Feulgen staining. Both diploid (2n=18, 28, 32, and 34) and tetraploid (2n=68) with extensive chromosome number variations including the occurrence of B-chromosomes (0–2Bs), and aneuploidy (2n=30 and 31 instead of 2n=32) have been found in Korean Carduus-Cirsium taxa. The karyotypes of the nine taxa, Cirsium japonicum var. spinissimum, C. schantarense, C. rhinoceros, C. nipponicum, C. setidens, C. vlassoviianum, C. lineare, C. pendulum, and Carduus crispus are reported here for the first time. While these reported chromosome numbers do not provide any delimitation at the sectional levels for the Korean Carduus-Cirsium taxa, karyotypes and chromosome size are well-conserved at the species level and thus, have taxonomic significance.