Data from: Responses of social and solitary bees to pulsed floral resources

Pulsed food resources lead to mismatches between distribution of consumers
and resources in space and time. Many studies have investigated how
pollinators and floral resources covary in space, but few have looked at
their covariance among years. I studied responses of two bee taxa, Bombus
(a social genus) and Anthophora (a solitary genus), to variation in
flowering by Astragalus scaphoides, a perennial herb that flowers in
alternate years. First, I quantified the rate at which individual plants
were visited by bees. Anthophora showed evidence of a demographic response
to resource pulses—that is, more individuals were seen in the year after a
high-flowering year—whereas Bombus did not. Second, I quantified
pollinator behavior by following individual bees and recording the
proportion of visits to A. scaphoides within single foraging bouts. The
proportion of visits to A. scaphoides by both taxa increased with A.
scaphoides’s flowering density. Higher specialization in high-flowering
years likely makes both taxa better pollinators in high-flowering years.
If these taxa differ in effectiveness as pollinators, then these responses
translate into variation in pollination services in space and time,
specifically, more activity by Bombus in high-flowering years and more by
Anthophora in years following high-flowering years. They also emphasize
that pollinator activity depends in part on past—as well as current—floral
resources.