UC San Diego
Interactions between squash bees (Peponapis prinosa) and honey bees (Apis mellifera) on winter squash (Cucurbita pepo)
- Author(s): Sandoval, Sara Shell
- Advisor(s): Holway, David
- et al.
This study focuses on interactions between the non-native western honey bee (Apis mellifera), which is a super generalist pollinator, and the native squash bee (Pepanapis pruinosa), which is specialist that solely depends on squash pollen to reproduce. This pollination system provides an opportunity to compare the behavior of specialist (Peponapis) and generalist (Apis) pollinators and how interactions between the two affect plant reproductive success. Using videos to record the behavior of Peponapis and Apis in the flowers of acorn squash (Cucurbita pepo), we found that compared to squash bees, honey bees had higher visitation rates and more frequently occupied flowers with multiple individuals. Accordingly, intra-floral interactions between honey bee individuals (both aggressive and non-aggressive) were more common than were interactions between squash bees and honey bees. Honey bees increased their visitation rate in response to increasing nectar volume unlike squash bees, which exhibited an independent relationship between visitation rate and foraging. Interestingly, honey bee foraging appeared to have both positive and negative effects on plant reproductive success. Seed number was negatively related to the cumulative time that honey bees spent on stigmas, whereas mean seed weight and fruit volume both increased with the frequency of aggressive interactions between honey bee individuals.