Quelques facteurs déterminant le comportement de butinage d'Hypotrigona pothieri (Trigonini) dans la végétation de Côte-d'IvoireD. Lobreau-Callena, A. Le Thomasb, B. Darchenc, R. Darchenc and N. D'Amicob
a CNRS et EPHE, Laboratoire de phanérogamie du Muséum, 16, rue Buffon, 75005 Paris, France
b Laboratoire de phytomorphologie de l'EPHE, 16, rue Buffon 75005 Paris, France
c Station biologique de l'université de Paris-VI, 24620 Les Eyzies, France
Abstract - Some factors determining foraging behaviour of Hypotrigona pothieri (Hym, Apidae) in the vegetation of Ivory Coast
Pollen analysis of crops from Hypotrigona pothieri Darchen (Hym, Apidae), social bees of the tribe Trigonini, were carried out on 7 hives installed in 5 different biotopes from woody savanna and from forest gallery in the region of Lamto. They were opened in July to August during the short dry season after a 5 month period. Their content is compared to one of a check hive in their original environment. The floristic inventory of the surroundings of these different hives is summarized in table I. The pollen extracted from honey, from pollen cells and from food supply was isolated and acetolysed. The quantity of pollen of each species from honey and from food supply is indicated in relative percentage of the total number of pollen grains for each sampling. In each case, 1 200 pollen grains were counted and identified (Vergeron, 1964). For the pollen cells, the abundance ratio is indicated and the content of the cells are analyzed individually (table II). The results indicate that, in spite of a rather extensive overall pollen spectrum, these social bees are generally opportunistic and fairly selective. They show a preference for a small number of plant species (dominant taxa, fig 1) always near the hives; the choice is independent of the type of flower structure but seems to be related to the presence of certain alkaloids in the nectars. These taxa are dominant taxa as much in the honey, as in the pollen cells or food supply. However, the quantities are different and the intermediate percentages noticed in the food supply show that they constitute a mixture of the two types of stores (honey and pollen). Pollen analysis of material from the two hives staying in the same biotope (R5a and R5b) show that the choice of the gathered species is directly influenced by the orientation of the entrance of nests. However, when the Hypotrigones are displaced in forest gallery, the pollen content from the stores and from the food supply shows these bees survive only if they are situated in open areas (R1, R4). In the case where the hives were placed in dense undergrowth (R3), the bees survive with difficulty, their brood is not renewed and the colony finally dies out. Light seems indispensable to the good functioning of hives of Hypotrigona, as indicated by the association of their normal nesting biology with open areas, such as savannas.
Key words: Hypotrigona pothieri / foraging behaviour / pollen analysis / ecology / Apidae