Data from: Foraging behaviour and pollination contribution of naturally occurring bumble bees in red clover

Pollinators optimise their foraging behaviours in response to changes in
floral rewards, which may consequently affect pollen transfer and plant
reproductive success, especially in plants that require cross-pollination.
In a red clover field grown for seed production, we conducted a three-year
experiment to compare the foraging behaviours of naturally occurring
bumble bee species and their pollination contributions. Specifically, we
investigated how the visitation of a flower head by one bumble bee may
affect the foraging behaviours of any second visiting bee. We also
measured relative abundance, stigmatic pollen deposition, and plant traits
including flowering intensity, corolla tube length, and seed set. We found
that bees can identify previously visited flower heads: the second
visiting bees increased their rejection probabilities with the flower
exploitation rate of the first visiting bees. The second bees also had a
higher foraging speed than the first visiting bees, either due to the
depletion of floral rewards or the reduced pressure required to trip the
florets. Among the five bumble bee species naturally occurred during the
peak flowering, different bumble bees showed varied preferences for the
co-flowering cultivars. At the flower head level, one visit from B.
pascuorum and B. muscorum was sufficient for the seed set, similar to the
seed set in the open pollination. However, B. hortorum that caused high
stigmatic pollen deposition did not result in comparable high seed set,
this might be related to a limited number of cross-pollen transferred,
caused by the abundant floral resources during the peak flowering, or an
intrinsic characteristic of this bumble bee species.