Pollinator diversity has long been associated with the reproductive success of both native and agricultural plants; however, recent studies argue that because pollinators vary widely in the quantity and quality of services they provide, the abundance of a few dominant species may be responsible for a majority of service provision. These findings highlight the importance of determining species-specific contributions to overall community and landscape function.
In this study, we investigate species-specific pollinator efficacy on cotton flowers and compare the quality and quantity of service provided by a full pollinator community to a subset of the community including only the five most dominant and effective pollinators.
Specifically, pollinator efficacy was determined for 58 hymenopteran species that visited cotton flowers over a thre-year period in the South Texas cotton growing region. Efficacy was calculated based on field and lab quantifications of the quantity (visitation rate) and quality of service (pollinator foraging behavior, timing of pollen deposition, number and suitable pollen grains carried, number of pollen grains deposited in a single visit).We then modeled service provision using a central place foraging model based on the InVEST program that incorporates nesting and floral preferences, nesting and floral resources available per land use type, and the cotton pollination efficacy of each species to estimate service provision to cotton across the South Texas cotton growing region.
Based on the quantity and quality of service, we found that the five most effective pollinators of South Texas cotton were: Apis mellifera, Melissodes tepaneca, Agapostemon texana, Diadasia diminuta, Halictus ligatus. Using our quantification of effectiveness, and nesting and floral preferences and availability to calibrate our InVEST model, we found that the loss of 90% of pollinator diversity (53 species) has a negligible effect on service provision in this system. The remaining five species (10%) provide indistinguishable levels of service provision in the region compared to the full community.
If conservation efforts hope to protect bee pollinators in this region, the delivery of crop pollination services is an insufficient argument for conservation. Conserving the biological diversity of bee therefore requires more than just an ecosystem service based argument.