Geographic Distribution of Diploids and Polyploids of the Ixeris chinensis Complex (Asteraceae; Lactuceae) in East Asia

Abstract

The distribution of di-, tri-, and tetraploids of the Ixeris chinensis complex in the East Asia is surveyed by determining the ploidy on the basis of pollen grain size and stainability. Diploids are restricted to Ixeris chinensis subsp. chinensis, and tri- and tetraploids to I. chinensis subsp. strigosa. In continental areas of the East Asia including Korea, all the di-, tri-, and tetraploids occur. In contrast, only diploids are found in Taiwan, while only tri- and tetraploids occur in Japan. The triploids in Japan seem likely to have migrated from the continental Asia, rather than they originated in Japan by hybridization between diploids and tetraploids, and have been distributed throughout Japan by agamic propagation.