Floral resource partitioning between native Melipona bees and the introduced Africanized honey bee in the Brazilian Atlantic rain forestW. Wilmsa, b and B. Wiechersa
a Zoologisches Institut der Universität Tübingen, Auf der Morgenstelle 28, 72076 Tübingen, Germany
b Departamento de Ecologia Geral, Universidade de São Paulo, 05508-900 Sâo Paulo, SP, Brazil
Abstract - Pollen and nectar harvested by colonies of two stingless bee species (Melipona bicolor and M quadrifasciata) and the Africanized honey bee (Apis mellifera) were monitored over a year in the Brazilian Atlantic rain forest. The spectrum of plants used for pollen by the Melipona species was rather restricted. Only five pollen types contributed more than 1% to the total harvest over the year. The most important plant families were Myrtaceae and Melastomataceae, which also provided most of the nectar. The Africanized honey bee mainly used plants of Myrtaceae, Asteraceae, Euphorbiaceae and Arecaceae for pollen and Cunoniaceae, Rubiaceae and Myrtaceae for nectar. Measures of trophic niche overlap indicate the importance of common resource utilization for all three species of eusocial bees. Niche overlap between Melipona bees and A mellifera was more evident for nectar than for pollen. However, the peak in pollen harvest by the colonies of stingless bees as revealed by the number of newly filled storage pots coincided with a low level of presumed competitive pressure of Africanized honey bees, which was calculated as a product of niche overlap and amount of resources harvested. This can be interpreted as indirect evidence of actual competition for food.
Key words: stingless bees / Africanized honey bee / Brazilian Atlantic rain forest / pollen analysis / resource exploitation / trophic niche overlap