Quantifying the pollination service supplied to pumpkins (Cucurbita pepo) by multiple bee species

Pumpkin production relies on insect-mediated pollination and our goal was to measure the contribution of key pollinators to this service. To accomplish this, we 1) determined how known amounts of pollen influence fruit set and seed production, 2) quantified the amount of pollen deposited by individual bee species, 3) observed the ambient diversity and abundance of bees visiting open female flowers, and 4) measured how seed production is influenced by pollinator community composition. We hypothesized that multiple pollinator species contribute to pumpkin pollination, and that the pollination service provided varies by species. We determined how known amounts of pollen influenced fruit set and seed production by hand-pollinating female flowers with 40, 150, 500 or 2000 pollen grains, allowed fruit to mature, and counted the number of seeds produced per fruit. We determined the amount of pollen deposited by individual bee species by allowing single pollinators to visit female flowers. These flowers were either collected following the pollinator visit to determine the number pollen grains deposited or bagged to prevent additional bee visits and seed production was measured in mature fruit. We measured the ambient diversity and abundance of pollinators that visit a female flower within a 7 h pollination window using video surveillance. From these data we determined how variation in the community of bees influenced both pollen deposition and seed set. Future work will examine how pollinator communities and pollination services are influence by the addition of floral resource strips to pumpkin production as a habitat management strategy.