Seasonality of floral resources in relation to bee activity in agroecosystems

• Published in: Ecology and evolution Vol. 11; no. 7; pp. 3130 - 3147
• Main Authors: Guezen, Jessica M., Forrest, Jessica R. K.
• Format: Journal Article
• Language: English
• Published: England John Wiley & Sons, Inc 01.04.2021; John Wiley and Sons Inc; Wiley
• Subjects: Abundance; Agricultural ecosystems; Agricultural land; agricultural landscape; Anthophila; Availability; Bees; Correlation analysis; Crops; Dilution; floral volume; Food availability; Hypotheses; Insects; Landscape; Life history; Nectar; Original Research; Plant reproduction; Pollen; Pollination; pollinators; Population; Populations; Resource availability; Seasonal variations; Seasons; spatiotemporal scale; Anthophila; agricultural landscape; spatiotemporal scale; floral volume; pollinators
• ISSN: 2045-7758; 2045-7758
• DOI: 10.1002/ece3.7260

The contribution of wild insects to crop pollination is becoming increasingly important as global demand for crops dependent on animal pollination increases. If wild insect populations are to persist in agricultural landscapes, there must be sufficient resources over time and space. The temporal, within‐season component of floral resource availability has rarely been investigated, despite growing recognition of its likely importance for pollinator populations. Here, we examined the visitation rates of common bee genera and the spatiotemporal availability of floral resources in agroecosystems over one season to determine whether local wild bee activity was limited by landscape floral resource abundance, and if so, whether it was limited by the present or past abundance of landscape floral resources. Visitation rates and landscape floral resources were measured in 27 agricultural sites in Ontario and Québec, Canada, across four time periods and three spatial scales. Floral resources were determined based on species‐specific floral volume measurements, which we found to be highly correlated with published measurements of nectar sugar mass and pollen volume. Total floral volume at varying spatial scales predicted visits for commonly observed bee genera. We found Lasioglossum and Halictus visits were highest in landscapes that provided either a stable or increasing amount of floral resources over the season. Andrena visits were highest in landscapes with high floral resources at the start of the season, and Bombus visits appeared to be positively related to greater cumulative seasonal abundance of floral resources. These findings together suggest the importance of early‐season floral resources to bees. Megachile visits were negatively associated with the present abundance of floral resources, perhaps reflecting pollinator movement or dilution. Our research provides insight into how seasonal fluctuations in floral resources affect bee activity and how life history traits of bee genera influence their responses to food availability within agroecosystems. If wild bee populations are to persist in agricultural landscapes, there must be sufficient floral resources over time and space. We ask whether the spatial and within‐season temporal availability of floral resources can predict bee activity in agricultural landscapes. We found that visits from sweat bees, mining bees, and bumble bees were best predicted by the amount of floral resources available previously in the season, while visits from leafcutter bees were best predicted by the current availability of floral resources.