Environmental and spatial filtering of ladybird beetle community composition and functional traits in urban landscapes

Abstract

Abstract Urban community gardens provide habitat for biodiversity within urban landscapes. Beneficial insects, those that provide important ecosystem services like pollination and pest control, are among the many inhabitants of these green spaces. Garden management and the composition of the urban matrix in which they are embedded can affect not only the abundance and species richness of beneficial insects but also their community composition and functional traits. During 2014 and 2015 (June to September), we collected ladybird beetles (Coleoptera: Coccinellidae) in 19 community gardens in three counties of the California Central Coast. We examined the effects of garden- and landscape-level characteristics on ladybird community composition and functional traits. Out of the 19 species collected, only 3 were non-native to California (3 were not identified to species). Similarities in ladybird species composition were not driven by geographic distance between gardens, which suggest that beetles in these landscapes are not experiencing dispersal limitation. Instead, three landscape-level environmental variables and seven garden-scale ones correlated with changes in community composition. Even though we perceive cities as highly disturbed low-quality landscapes, our results suggest that highly mobile arthropods such as ladybird beetles, may not perceive the urban matrix as a barrier to movement and that urban gardens can be inhabited by native species with different sizes, diet breadths and diets. Nevertheless, our results also suggest garden specific management practices, such as altering ground cover, can affect the taxonomic and functional composition of ladybird beetles with potential implications to their ecosystem services.