Wild bee functional diversity and plant associations in native and conventional plant nurseries

Abstract

1. An ongoing challenge in ecology is predicting how characteristics of communities correspond to habitat features. Examining variation in functional traits across species may reveal patterns not discernible from measures of mere abundance or richness. For beneficial insects like wild bees, functional trait‐based approaches are often used to characterise communities in different agricultural habitats.2. However, no such approach has yet been applied in horticultural plant nurseries, which represent intensively managed artificial flowering plant assemblages. Certain nurseries mostly cultivate regionally native flowering plants, allowing one to test how differences between local plant assemblages may correlate with bee functional traits.3. We surveyed bee assemblages at native and conventional plant nurseries in southern California from spring through autumn over 2 years, while also documenting the native status of blooming plants in sampling plots. Bees were classified into different functional categories based on their diet breadth, nesting location, and social organisation.4. At native plant nurseries, we netted proportionally more specialist bee species and fewer generalist species than at conventional nurseries. Nesting location and social organisation of bee samples did not differ between nursery types. Meanwhile, landscape‐level features were not associated with any observed functional trait metrics of bee collections. Furthermore, network‐level specialisation of bee‐plant interactions was higher at conventional nurseries.5. Our results suggest that a horticultural cultivation practice is quantifiably correlated with the functional distribution of resident bee assemblages. These results are important and encouraging to pollinator conservation efforts in nursery systems and other human‐modified landscapes dominated by ornamental plants.