Foraging strategy predicts species-specific patterns of pollen foraging
by honey bees and bumble bees
Abstract
Honey bees and bumble bees are generalist eusocial bees that collect
resources from a variety of plant taxa. Both bee species have distinct
foraging strategies that affect patterns of resource collection, with
implications for designing pollinator friendly habitat management
schemes. Using a comparative approach, we examined the pollen foraging
patterns of the honey bee (Apis mellifera) and common eastern bumble bee
(Bombus impatiens) in a suburban-agricultural landscape. We tested
predictions stemming from the bees’ known foraging strategies of dance
communication or trapline foraging, respectively, and collected pollen
from returning foragers of each bee species over five time periods at
each of three sites. We quantified the frequency of flower constant
foragers, the richness and diversity of pollen collected by a colony,
and whether honey bees or bumble bees show preferences by comparing the
taxonomic identity of pollen collected to resources available. Analyses
were done at the pollen morphotype and plant family levels. Within a
foraging trip, honey bees foraged on a single plant family more
frequently than bumble bees throughout the summer, except during July,
when both species demonstrated a similar frequency of flower constancy.
Pollen diversity was greater for bumble bees relative to honey bees, and
both bee species collected less diverse pollen in June. Finally, bumble
bees preferred the Fabaceae_Tricolporate pollen morphotype (Trifolium
repens or Medicago sativa), but avoided Apiaceae, while honey bees
foraged randomly showing no evidence of preference. These results
support the hypothesis that species level foraging strategies affect how
bees exploit pollen resources. Explicitly considering pollinator
foraging strategy when designing agri-environment schemes will inform
the most appropriate arrangement of floral resources within developed
landscapes, thereby promoting both pollinator health and pollination
services of bee-dependent crops.