The currently recognized eastern Asian-North American disjunct species A. pedatum needs to be segregated into three species, corresponding to populations in eastern North America, China, and Japan. The eastern Asian-North American disjunction in the complex is inferred to be the result of two intercontinental migrations, one from eastern Asia into North America in the late Tertiary and the other from North America back to eastern Asia in the Pleistocene.
-The chromosome numbers and karyomorphology of 14 Chinese species of the genus Parnassia were investigated. The chromosome numbers of 11 species were reported for the first time. The report of 2n=48 for P. monochrofolia Franch was new to the Chinese species of the genus. There are about 30 species cytologically studied up to now. From the available data, the species of Parnassia with the basic chromosome numbers of x=7, 8 and 9 were found in China and the Himalayas, in which the more species with x=9, as well as mainly in western N America, while x=8 was only found in eastern N. America. Polyploidization was common in the genus, more extensively in Northern America. Based on our results and the previously reported data, the basic chromosome numbers and polyploidization are discussed. Combined with gross morphology and geographical distribution of Parnassia, the phylogenetic implications of the cytological data are also discussed. It is suggested that eastern Asia and western N America are probably the modern divergent centers of the genus.
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