GERMINATION, PREDATION AND DISPERSAL OF ACACIA-ALBIDA SEEDS

Infestation rates by bruchid beetles on Acacia albida seeds in Southern Province, Zambia were found to be 13.1% for seeds collected early in the fruiting season and 8.9% in late season. There was no indication of reinfestations by bruchids. Seeds from dry cow dung were found to be intact (65%) or decayed (35%), suggesting that all bruchid-infested seeds were killed in the guts or in the cow dung. Untreated seeds from pods had very low germination (2%), but were almost all alive, as indicated by the high germination when scarified. Seeds from cow dung behaved similarly. Therefore, all seeds that were able to germinate at defecation had subsequently died in the dung. Seeds with visible bruchid exit holes had a high germination rate if collected early in the season, but were all dead later in the season. Pods kept under water did not sink for a week, and water-soaked seeds remained alive for up to 16 days, suggesting that water dispersal may locally play a role in the dispersal of A. albida seeds. Survival chances for cattle-dispersed and un-dispersed A. albida seeds were calculated from the proportions of intact and damaged seeds, death rates in cow dung, and germination rates obtained in this experiment, combined with estimates from other studies. Seed survival when dispersed by cattle seemed to be equal or lower than when not dispersed.