Karyotypes in four species of Ranunculus (Ranunculaceae): Karyotypic variation in Mainland China and the Japanese Archipelago

摘要

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.