Calamagrostis hakonensis (Poaceae): Distribution and differentiation of cytotypes |
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Authors: | Tuguo Tateoka |
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Institution: | (1) Department of Botany, National Science Museum, Sakura-mura, 305 Ibaraki |
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Abstract: | Chromosome counts were made for a total of 540 collections ofCalamagrostis hakonensis from 66 localities ranging from Kyushu to Hokkaido. Distribution and habitat preferences of the cytotypes involved are described.
Sympatric occurrence of tetraploids (=semidiploids, 2n=28) and higher polyploids, as well as that of septaploids and plants
at hexaploid and/or octoploid levels, was confirmed in several localities, and mixtures of hexaploids and octoploids within
a population were frequently observed. Plants at hexaploid and octoploid levels were the most abundant and widespread. An
examination of pollen of the voucher specimens showed that tetraploids (amphimictic) had good pollen, while higher polyploids
(apomictic) were generally devoid of pollen and very rarely produced moderately good pollen, the grains of higher polyploids
being larger than those of tetraploids. Distributions of tetraploids and higher polyploids were more precisely delineated
through an examination of pollen of many herbarium specimens. In relation to the processes by which the complicated internal
structure ofC. hakonensis has been established, the following subjects are discussed: infraspecific hybridization between ecotypically differentiated
populations, enrichment of variability through occasional sexual reproduction expected in plants with more than 2n=42, persistence
of the variants by apomictic reproduction, and probable roles of some extinct taxa. |
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Keywords: | Apo-amphimictic complex Calamagrostis hakonensis Distribution of cytotypes Infraspecific hybridization Polyploid evolution |
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