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TYBIRK, K., 1993. Pollination, breeding system and seed abortion in some African acacias. Studies of the flower visitors and pollination ecology of Acacia albida Del., A . nilotica (L.) Willd. ex Del. A . tortilis (Forssk.) Hayne and A . senegal (L.) Willd. in Senegal and Kenya showed a high diversity of floral foragers. One hundred and eighteen taxa of insects mainly from Hymenoptera, Lepidoptera, Coleoptera and Diptera were collected. The most important pollen vectors were bees from the families Megachilidae and Halictidae, and wasps from the families Scoliidae and Eumenidae. Beetles, flies and butterflies were secondary pollen vectors. Diversity and frequency of flower visitors of species with floral nectar ( A . senegal and A . albida) were not clearly different from species without floral nectar ( A . tortilis, A . nilotica). Acacia tortilic was almost exclusively outcrossed (Index of Self Incompatibility = 0.2), with 5.5% of the inflorescences (0.13% of the flowers) developing fruits. The number of seeds per pod was positively correlated with dispersal type. Wind dispersed species had fewer seeds per pod than animal dispersed species. About 5% of the seeds were aborted in A . fortilis and A . nilotica, while 2211.8% of the seeds were aborted in A . senegal, A . ataxacantha DC. and A . polyacantha Willd. Most abortions in the latter three species occur in the proximal end of the pods, indicating selective seed abortion.

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No abstract

TYBIRK, K., 1993. Pollination, breeding system and seed abortion in some African acacias. Studies of the flower visitors and pollination ecology of Acacia albida Del., A . nilotica (L.) Willd. ex Del. A . tortilis (Forssk.) Hayne and A . senegal (L.) Willd. in Senegal and Kenya showed a high diversity of floral foragers. One hundred and eighteen taxa of insects mainly from Hymenoptera, Lepidoptera, Coleoptera and Diptera were collected. The most important pollen vectors were bees from the families Megachilidae and Halictidae, and wasps from the families Scoliidae and Eumenidae. Beetles, flies and butterflies were secondary pollen vectors. Diversity and frequency of flower visitors of species with floral nectar ( A . senegal and A . albida) were not clearly different from species without floral nectar ( A . tortilis, A . nilotica). Acacia tortilic was almost exclusively outcrossed (Index of Self Incompatibility = 0.2), with 5.5% of the inflorescences (0.13% of the flowers) developing fruits. The number of seeds per pod was positively correlated with dispersal type. Wind dispersed species had fewer seeds per pod than animal dispersed species. About 5% of the seeds were aborted in A . fortilis and A . nilotica, while 2211.8% of the seeds were aborted in A . senegal, A . ataxacantha DC. and A . polyacantha Willd. Most abortions in the latter three species occur in the proximal end of the pods, indicating selective seed abortion.