Consequences of Introduced Honeybees Upon Native Bee Communities

Abstract

Biological invasions represent both an increasingly important applied problem and a tool for gaining insight into the structure of ecological communities. Although competitive interactions between invasive and native species are considered among the most important mechanisms driving invasion dynamics, such interactions are in general poorly understood. The European honey bee (Apis mellifera) is a widespread and economically important invader that now has a near-global distribution long suspected to competitively suppress many native bee species. Besides, various bumblebees (Bombus sp.), the alfalfa leafcutter bee Megachile rotundata, and various other solitary species have been introduced to countries far beyond their home range. Possible negative consequences of these introductions include: competition with native pollinators for floral resources; competition for nest sites; co-introduction of natural enemies, particularly pathogens that may infect native organisms; pollination of exotic weeds; and disruption of pollination of native plants. Interspecific competition for a limited resource can result in the reduction of survival, growth and/or reproduction in one of the species involved. As the impact of honey bees on native bees depends on the resource quality and quantity, it is recommended to assess the habitat quality in relation to its fauna by experts before any introduction of bee hives to deduce the number of hives, which can be introduced with a minimum impact. Thomson (Ecology 85:458–470, 2004) reported that Bombus occidentalis colonies exposed to competition with Apis experienced increased nectar scarcity and responded by reallocating foragers from pollen to nectar collection, resulting in lowered rates of larval production. These results provide evidence that Apis competitively suppresses a native social bee known to be an important pollinator, with the potential for cascading effects on native plant communities. Likewise introduction of Apis mellifera eliminated Apis cerana japonica in China and Japan and Apis cerana indica in Indian subcontinent including India, Pakistan, Nepal, Bangladesh and other neighbouring countries. How Apis influences native communities is of particular interest in light of both growing concerns over declines of many native pollinator species and uncertainty about the implications of disease-driven Apis declines and the spread of Africanized Apis strains. Negative impacts of exotic bees need to be carefully assessed before further introductions are carried out.