Karyotype analysis and taxonomic insights of <i>Cirsium</i> (Compositae) in Taiwan

This study conducted a comprehensive karyotype analysis of Cirsium (Compositae) species in Taiwan to elucidate their taxonomic relationships. This study investigated 12 known Cirsium taxa indigenous to Taiwan. Notably, detailed karyotype analyses of all Taiwanese taxa are reported for the first time, with the karyotypes of four taxa, C. ferum, C. japonicum var. fukienense, C. suzukii, and C. arisanense f. purpurescens, documented for the first time in this study. The chromosome numbers of Taiwanese Cirsium species mostly had a configuration of 2n=34, although instances of 2n=30 and 2n=32 were also observed. The karyotype analysis revealed differences in karyotype structures, asymmetry, and presence of satellite chromosomes between the taxa; these three characteristics are thus of considerable taxonomic import. To further explore karyotypic diversity among Taiwanese Cirsium species, this study used the unweighted pair group method with the arithmetic mean method in a cluster analysis and implemented principal component analysis. Our findings offer novel insights into the classification of Cirsium species and emphasize the critical role of satellite chromosomes in taxonomy, particularly for C. suzukii, C. taiwanense, and C. ferum.