Competition for floral resources drives the differentiation of foraging
strategy among three dominant bumble bees in an eastern Himalayan meadow
An understanding of the influence of competition on bumble bees’
foraging strategy is essential to understand the coexistence of multiple
bee species in the context of pollinator declines, but remains unclear.
We conducted a field survey in an isolated meadow in eastern Himalaya
with10 bumble bee species and more than 55 flowering plants they
visited. In 2018 and 2019 we measured abundance of the three dominant
bumble bees (one mainly foraging for pollen and two for nectar) and
recorded the identity and frequency of flowering plants they visited.
The intensity of competition of species pairs was evaluated by niche
overlap. A composite index of flower depth of plants visited by each
bumble bee was calculated on each sampling day. Results indicated that
foraging strategies of the three bee species shifted differentially in
response to increasing competition; the pollen-seeking bee was forced to
forage for more nectar while the nectar-seeking bees were impelled to
change target flowers in order to match proboscis length and flower
depth. The coexistence of multiple bumble bee species in a community can
thus be achieved by adjusting foraging strategy in response to intensity
of competition for floral resources.