AOBPreview originally published online on August 23, 2008
Annals of Botany 2008 102(5):747-755; doi:10.1093/aob/mcn157
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Pollination Systems of Colchicum (Colchicaceae) in Southern Africa: Evidence for Rodent Pollination
1 Department of Botany, University of Cape Town, Rondebosch 7700, South Africa
2 School of Biological and Conservation Sciences, University of KwaZulu-Natal, P Bag X01, Scottsville, Pietermaritzburg 3209, South Africa
* For correspondence. E-mail ckleizen{at}gmail.com
Received: 21 May 2008 Returned for revision: 27 June 2008 Accepted: 21 July 2008 Published electronically: 23 August 2008
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.
Key words: Convergent evolution, floral syndrome, pollination, rodents, birds, insects, Colchicum scabromarginatum, Colchicum coloratum, Succulent Karoo, southern Africa
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