Phylogeny and radiation of pollination systems in DISA (Orchidaceae) |
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Authors: | Johnson S Linder H Steiner K |
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Institution: | 1. Department of Botany, University of Cape Town, Rondebosch 7700, South Africa;2. Compton Herbarium, National Botanical Institute, P. Bag X7, Claremont 7735, South Africa |
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Abstract: | We studied the patterns of adaptive radiation in Disa, a large orchid genus in southern Africa. A cladogram for 27 species was constructed using 44 morphological characters. Pollination systems were then mapped onto the phylogeny in order to analyze pathways of floral evolution. Shifts from one pollination system to another have been a major feature of the evolutionary diversification of Disa. Unlike many plant genera that are pollinated mainly by a single group of insects, radiation in Disa has encompassed nearly all major groups of pollinating insects; in all, 19 different specialized pollination systems have been found in the 27 species included in this analysis. Another striking pattern is the repeated evolution of broadly similar pollination systems in unrelated clades. For example, butterfly-pollinated flowers have evolved twice; showy deceptive flowers pollinated by carpenter bees, twice; long-spurred flowers pollinated by long-tongued flies, four times; night-scented flowers pollinated by moths, three times; and self-pollination, three times. This suggests that a few dominant pollinator species in a region may be sufficient to generate diversification in plants through repeated floral shifts that never retrace the same pathways. |
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Keywords: | adaptive radiation cladistics convergent evolution Disa floral adaptation Orchidaceae pollination speciation |
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