New diploid populations of the Chrysanthemum zawadskii complex (Asteraceae) in natural habitats of Korea

Abstract

Chrysanthemum zawadskii Herbich is widely distributed from northern Europe to East Asia. It has been reported that various ploidy levels ranging from diploid (2n = 2x = 18) to decaploid (2n = 10x = 90) are distributed in Korea. The diploid populations of C. zawadskii, however, have limited habitats, with only four populations from two locations compared to polyploids that are widely distributed in Korea. During recent biodiversity research on the C. zawadskii complex, new habitats of diploid populations of C. zawadskii not reported earlier in Korea were identified. To understand the speciation mechanism accompanying polyploidization of the C. zawadskii complex, it was necessary to investigate the features of these new populations as to whether they identical to or different from previously reported diploid populations. For this purpose, we identified the number and karyotypes of somatic chromosomes in four new diploid populations and compared the morphological features. It was found that the new diploid populations differed slightly in terms of the size and color of the flowers and in the shape of the leaves, with continuous variations. Representative karyotypes of the new populations were included in previously reported diploid karyotypes, but the numbers and locations of satellite chromosomes differed. In addition, we found that one of them is a sympatric population with different ploidy levels, including diploid, tetraploid, and hexaploid. From these results, it was confirmed that morphological and cytological variations exist among diploid populations in the C. zawadskii complex.