Abstract
Five species of Ranunculus such as R. brotherusii, R. sieboldii, R. chinensis and R. silerifolius were karyologically studied especially with respect to speciation. Ranunculus brotherusii had the karyotype of 32 small-sized chromosomes (x=8). Ranunculus sieboldii had two different cytotypes such as 2n=48 and 2n=64. The 2n=48 karyotypes of the species from Mainland China were similar to each other and were identical to the 2n=48 karyotype from the Japanese Archipelago. The 2n=48 karyotype consisted of two different chromosomal groups: One chromosomal group comprising 32 and the other chromosomal group comprising 16 chromosomes. The 2n=64 karyotype might be produced by the fertilization of a normal gamete and an unreduced gamete. The karyotypes of R. sieboldii evidenced that the hybridization might play an important role of speciation. Ranunculus chinensis had a single and stable karyotype with 2n=16 under a wide geographical distribution across Mainland China and the Japanese Archipelago. In R. silerifolius specimens from the Mainland China, two different karyotypes such as Mugi and Otaru-C were identified. The Mugi cytotype was widely distributed across Mainland China and the Japanese Archipelago. The new karyotype, Otaru-C, was proposed in specimens from Mainland China. Polymorphism of the cytotype in R. silerifolius in the Japanese Archipelago was pointed out as an example of sympatric speciation.
