Arthropods in urban agroecosystems Seattle 2019

Like other urban green spaces, urban community gardens can act as
biodiversity refugees, especially for small organisms like arthropods. In
turn, arthropods can provide important ecosystem pest control services to
these agroecosystems. Thus, an often-asked question among urban gardeners
is how to improve gardens and surrounding areas for natural enemies and
associated pest control services. We examine how local vegetation and
garden characteristics, as well as the surrounding landscape composition
affect ground-dwelling beetles (Coleoptera: Carabidae and Staphylinidae),
spiders (Aranea), opilionids (Opilionida), and ladybird beetles
(Coleoptera: Coccinellidae), all of which are important predators. In the
summer 2019, we collected predators, vegetation, ground cover, and garden
and landscape characteristic data of ten community gardens in the city of
Seattle, Washington. We found that different groups of natural enemies are
associated with different environmental variables and at different scales;
probably related to differences in their dispersal capabilities, habits,
and diets. Floral variables (# of flowers, # of species in flower) had a
negative effect on non-flying natural enemies (spiders, opilionids, and
ground-dwelling beetles), but not on flying ones (ladybird beetles). The
only taxa that was significantly affected by a landscape-scale variable
was Opilionida, the only group examined that exclusively disperses by
ground. Our results show contrasting results to similar studies in
different regions and highlight the need to expand the taxa and regions of
study.