Journal Article

Pollination Systems of <i>Colchicum</i> (Colchicaceae) in Southern Africa: Evidence for Rodent Pollination

Ciara Kleizen, Jeremy Midgley and Steven D. Johnson

in Annals of Botany

Published on behalf of The Annals of Botany Company

Volume 102, issue 5, pages 747-755
Published in print November 2008 | ISSN: 0305-7364
Published online August 2008 | e-ISSN: 1095-8290 | DOI: http://dx.doi.org/10.1093/aob/mcn157
Pollination Systems of Colchicum (Colchicaceae) in Southern Africa: Evidence for Rodent Pollination

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Background and Aims

Plants adapted for pollination by rodents tend to exhibit a distinct floral syndrome that includes dull coloured and geoflorous inflorescences and nocturnal anthesis and nectar production. On the basis of their floral traits, it was predicted that two African Colchicum species (C. scabromarginatum and C. coloratum) are rodent-pollinated.

Methods

Field studies were carried out in the semi-arid Succulent Karoo region of South Africa. Live trapping of rodents was conducted and pollen loads on the rodents were quantified. The daily periodicity of nectar production was determined. Selective exclusion and controlled pollination experiments were also conducted.

Key Results

Live-trapped rodents were found to carry large amounts of Colchicum pollen on the fur of their snouts, and in their faeces. Birds were occasional pollinators of flowers of C. coloratum. During the evening, nectar volume and concentration increased for both species. When vertebrates were excluded from C. scabromarginatum and C. coloratum plants, there was a significant decrease in seed set compared with open control plants. By contrast, vertebrate exclusion did not significantly affect seed production of a congener, C. hantamense, which has floral traits associated with insect pollination. Breeding system experiments revealed that both C. scabromarginatum and C. coloratum require pollinators for seed production. Colchicum scabromarginatum is strictly self-incompatible, whereas C. coloratum is partially self-compatible.

Conclusions

Pollination by rodents occurs in two African Colchicum species. C. scabromarginatum appears to depend exclusively on rodents for seed production, while birds and autonomous selfing may contribute to seed production in C. coloratum. These are the first records of rodent pollination in the Colchicaceae.

Keywords: Convergent evolution; floral syndrome; pollination; rodents; birds; insects; Colchicum scabromarginatum; Colchicum coloratum; Succulent Karoo; southern Africa

Journal Article.  4753 words.  Illustrated.

Subjects: Ecology and Conservation ; Evolutionary Biology ; Plant Sciences and Forestry

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