EFFECTS OF HONEY-BEES ON COLONIES OF EXONEURA-ASIMILLIMA, AN AUSTRALIAN NATIVE BEE

Honey bee hives were placed, during two consecutive summers, in an experimental site which contained natural and artificially placed colonies of Exoneura asimillima, a semi-social, native bee. Two classes of colonies were studied: founders, and established colonies. Nests and contents were collected from an experimental site and three control sites following several months of exposure at the experimental site to the apiary honey bee population. Nest contents were analysed for differences among sites in colony population parameters which could have been caused by resource competition with introduced honey bees. Colony founding and overall colony survival were also considered. During the first season, the average number of large larvae plus prepupae per colony was significantly higher in the experimental site than in the control site. This difference could, however, have been the result of a two-week gap in sampling all the sites. All nest parameters showed high variability and there were no other significant differences between the two kinds of site. In the experimental site during the second season there were, relative to the control sites, significantly fewer total numbers of adult males and females in established nests and in all nests combined, significantly more immatures of all stages in founder nests and significantly lower adult male:female ratio. Although preliminary in nature, the data suggest that, in the experimental plots, E. asimillima showed: (i) increased adult emigration, (ii) increased brood rearing success, and/or (iii) relatively later colony founding, compared to the three controls. The possibility of resource competition with honey bees causing the observed changes is discussed, along with alternative explanations.