PS 1-3 - Pollinator behavior in community orchards varies along an urbanization gradient

Abstract: Pollinators play an integral role in the ecological development of the habitats they occupy due in part to their ecosystem services. Pollination services contribute to billions of dollars in crop production, including some of the most nutritious foods that we eat. In urban food deserts, these services are particularly important as communities often rely on pollination by wild pollinators in community gardens for fresh fruits and vegetables. Pollination services are influenced by many factors, including pollinator density, identity, and behavior. In human-dominated landscapes, pollinators may behave differently if they search farther distances among patches of flowers, which may in turn affect pollination success and fruit production. In this study, we examined the effects of urbanization on pollinator behavior in urban, suburban, and exurban community orchards in St. Louis, MO. Exurban, suburban, and urban environments were categorized based on the following socio-environmental variables: impervious surface area, woody tree cover, grassland/lawn cover, human population density, and housing density. We video-recorded clusters of flowers on randomly selected flowering fruit trees in 9 St. Louis community orchards (three locations in each socio-environmental category) for 1-2 hours (mean video length = 1.7 hours), weather depending. We assessed and tested for differences among socio-environmental categories in visitation rate, mean visit duration, and frequency of specific behaviors. Pollinator behavior varied across socio-environmental contexts and by pollinator type. Trees in urban orchards were more likely to be visited (67% of videos recorded at least one visit) relative to trees in suburban (54% of videos) and exurban (37% of videos) orchards. Bees in suburban sites exhibited longer visits relative to exurban orchards, but there was no difference relative to urban orchards. Visit duration of flies was not different among orchards and were generally longer than bee visits. Bees, which are collecting pollen for their developing young, may be more sensitive to changes in landscape parameters that influence flower resource availability, whereas flies, which only collect nectar for their own energetic needs, may be more strongly impacted by availability of larval hosts. Shorter, more frequent visits by bees may result in higher quality pollination of fruit trees in urban orchards relative to those in other human-dominated contexts. We discuss the implication of our result for fruit tree production in community orchards. Our results suggest that urban landscapes support important ecosystem services that can be leveraged to increase food access and production.