Phenological Floral Resource Complementarity is Important for Bee Abundance

Abstract

Spatial resource heterogeneity has been found to greatly influence the dynamics between diversity and function. This is particularly relevant for bee diversity and pollination services. While there has been ample research conducted to investigate these patterns, the impact of phenological resource heterogeneity (differences in availability of resources throughout time) on biodiversity and functioning has been less explored. This is important in agricultural systems, as many foraging periods of bees extend beyond the crop flowering event. In this study, we sought to understand how the bee community changed between seasons and if phenological complementarity of non-crop floral resources influenced bee diversity and abundance. We explored these questions in a region dominated by coffee agroecosystems in Mexico. This region was an ideal system for this study because the landscape offers a range of coffee management regimes that maintain heterogeneity in floral resource availability temporally and spatially. We found that the bee community varies significantly between the seasons. There were a greater proportion of native social bees in the rainy season than the dry season. The proportion of solitary bees did not vary between the seasons. Managed social bees had a significantly greater proportion in the dry season when coffee was flowering than all other sampling times. Additionally, we found that floral resources from groundcover, but not trees, were associated with bee abundance. However, the phenological scale of the availability of these resources is important, whereby contemporaneous resource availability appears particularly important in maintaining high bee abundance at sites with lower phenological complementarity through time. We argue that in additional to spatial resource heterogeneity, resource heterogeneity through time is also critical in explaining patterns in the bee community. Farms can support pollinator services and conservation by maintaining complementarity in floral resources available from both crop and non-crop plants.