I. Steffan-dewenter et T. Tscharntke, Resource overlap and possible competition between honey bees and wild beesin central Europe, OECOLOGIA, 122(2), 2000, pp. 288-296
Evidence for interspecific competition between honey bees and wild bees was
studied on 15 calcareous grasslands with respect to: (1) foraging radius o
f honey bees, (2) overlap in resource use, and (3) possible honey bee effec
ts on species richness and abundance of flower-visiting, ground-nesting and
trap-nesting wild bees. The grasslands greatly differed in the number of h
oney bee colonies within a radius of 2 km and were surrounded by agricultur
al habitats. The number of flower-visiting honey bees on both potted mustar
d plants and small grassland patches declined with increasing distance from
the nearest apiary and was almost zero at a distance of 1.5-2.0 km. Wild b
ees were observed visiting 57 plant species, whereas honey bees visited onl
y 24 plant species. Percentage resource overlap between honey bees and wild
bees was 45.5%, and Hurlbert's index of niche overlap was 3.1. In total, 1
849 wild bees from 98 species were recorded on the calcareous grasslands. N
either species richness nor abundance of wild bees were negatively correlat
ed with the density of honey bee colonies (within a radius of 2 km) or the
density of flower-visiting honey bees per site. Abundance of flower-visitin
g wild bees was correlated only with the percentage cover of flowering plan
ts. In 240 trap nests, 1292 bee nests with 6066 brood cells were found. Nei
ther the number of bee species nor the number of brood cells per grassland
was significantly correlated with the density of honey bees. Significant co
rrelations were found only between the number of brood cells and the percen
tage cover of shrubs. The number of nest entrances of ground-nesting bees p
er square metre was not correlated with the density of honey bees but was n
egatively correlated with the cover of vegetation. Interspecific competitio
n by honey bees for food resources was not shown to be a significant factor
determining abundance and species rich ness of wild bees.