Cytogeography of the Adiantum pedatum Complex (Pteridaceae, Subfamily Adiantoideae)

概要

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A chromosomal survey revealed that Japanese populations of the Adiantum pedatum complex (Pteridaceae, subfamily Adiantoideae) include four cytotypes: diploids of 2n=58 (x=29) and 2n=60 (x=30), and tetraploids of 2n=118 and 2n=120 (x=30). The few North American plants we analyzed were diploid (2n=58) and triploid (2n=87) (x=29). The two tetraploid cytotypes in Japan and the triploid from Canada are new cytotypes for this complex. In Japan, diploids with 2n=60 are widely distributed at all elevations throughout Hokkaido, Honshu and Shikoku. Diploids with 2n=58 are known from only two lowland sites in eastern Hokkaido. Tetraploids plants with 2n=118 and 120 are rare in the high mountains of central Honshu and a tetraploid plant with 2n=118 is known from a lowland site in central Hokkaido. Asian members of the A. pedatum complex have a base chromosome numbers of both x=29 and 30, whereas North American plants are known to have only x=29 as a base number. Since x=30 is considered to be ancestral in Adiantum, it is inferred that the x=29 cytotype in the A. pedatum complex originated in Asia and plants with this number later migrated to North America. Other possibilities are that plants with x=30 went extinct in North America, or they have yet to be found.
日本植物分類学会の論文
2005-04-11