Investigating the pollination of African baobab (Adansonia digitata .L) flowers by dayflying insects in South Africa

Abstract

The African baobab (Adansonia digitata L.) is a versatile tree known for its multiple uses in Sub-Saharan Africa. It provides people and animals with food, shelter and other materials. Many people in African countries sell baobab fruit to generate income. Therefore, assessing factors affecting fruit production, such as pollination, is essential. Baobabs has "chiropterophilous" flowers that are adapted to nocturnal pollination. While established research found that fruit bats pollinate baobab flowers in West and East Africa, recent evidence suggests Hawkmoths to be the likely pollinators in Southern Africa. Observations of diurnal insects visiting baobab flowers prompted questions about the effect of these insects on baobab pollination. However, the impact of dayflying insects has yet to be investigated. Therefore, this study specifically focuses on determining if dayflying insects play a role in the pollination of baobab, particularly their foraging behaviour and activity. The study first provides an overall literature review of the significance of pollination in baobabs, the shift of pollination systems, and determining the role of dayflying insects in pollinating baobab flowers in the morning. Secondly, using camera traps, we recorded all floral visitors and their foraging activity on baobab flowers in the morning between 4 am and 7 am. We determined how time, species and temperature affect the activity of dayflying insects. Hand pollination results indicated that the stigmas were still receptive and the pollen was still viable when the dayflying insects visited the flowers in the morning. Open-pollinated flowers showed that dayflying insects do not pollinate baobab flowers. Hymenopterans visit baobab flowers in the morning to collect pollen but do not function as pollinators. We also observed the changing composition of bee species over the 4 am to 7 am period, indicating the difference in the timing of the foraging activity of different insects. Our results support the hypothesis that daytime insects are unlikely to contribute to baobab pollination and that in South Africa, pollination seems to be dominated by hawkmoths. Nonetheless, diurnal insects still benefit from baobab flowers in terms of food.