科研之友
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摘要
The chromosome cytology of Hyacinthaceae subfamily Ornithogaloicleae is reviewed within the framework of a recent molecular-based classification, with particular emphasis on its center of diversity in sub-Saharan Africa. We also provide new chromosome counts for sections that are unknown or poorly known cytologically. Albuca subgen. Namibiogalum (9 spp.) probably has an ancestral base number of x=10 but subgen. Albuca ( 70 spp), subgen. Monarchos (9 spp.) and subgen. Osmyne (36 spp.) have x=9. The pattern in subgen. Urophyllon (3 spp.) is remarkable: although x=6 is likely, the species in the section exhibit a range of 2n=12, 10, 8, 6 and 4 (exclusive of polyploidy). All karyotypes have three large chromosome pairs and a variable number of small chromosomes. Pseudogaltonia (2 spp.) has x=9 and Dipcadi (26 spp.) possibly x=9 in series Uropetalum and x=6 in series Dipcadi, which exhibits a pattern of descending dysploidy leading to n=3 in D. marlothii. In Ornithogalum (+/- 130 spp.) chromosome numbers are known for only 24 of the 84 sub-Saharan species, mostly from subgen. Aspasia and subgen. Ornithogalum sect. Linaspasia, both of which have x=6, and from subgen. Galtonia, which has x=8. In contrast, x=7 is basic for the Eurasian sects. Honorius and Melophis, and x=18 seems likely for sect. Cathissa. Sect. Ornithogalum, the cytology of which we does not examine in detail, may have x=9. Polyploidy is apparently rare in the sub-Saharan African ornithogaloids, in marked contrast to the high frequency of polyploidy among Eurasian species. In Albuca just 3 or possibly 4 sub-Saharan species (9% or 13% of those counted) are exclusively polyploid and 5 more have diploid and polyploid races; and in sub-Saharan Ornithogalmn, only the tropical O. gracillimum is exclusively polyploid, and the western southern African O. hispidum has diploid and polyploid races.
- 出版日期2011-8
