Edge effects on parasitoid hymenopteran biodiversity in canola fields

Abstract

Parasitoid hymenopterans are highly valuable pest control agents. Despite their necessity within the agriculture industry, they remain one of the most understudied groups of insects. Non-crop habitats adjacent to farmland provide critical ecological services for these beneficial insects and can act as a corridor from uncultivated land to fields; this interaction is a form of edge effect. Here, we evaluate how 3 types of non-crop field edges affected the diversity, richness, and abundance of parasitoid hymenopterans at varying edge distances in canola (Brassica napus L.; Brassicales: Brassicaceae). We also compiled all sampled genera into a survey of parasitoid Hymenoptera found in southern Alberta canola. We conclude: (1) non-crop boundaries have a weak effect on parasitoid communities within our study system; (2) variability in parasitoid diversity and composition was most pronounced among farms, suggesting a dominant role of farm management practices; (3) parasitoid diversity is highest at edge boundaries and decreases toward the field interior; (4) Diolcogaster spp. (Hymenoptera: Braconidae)—predominantly Diolcogaster claritibia Papp, first reported in Canada in 2014—was the dominant group of parasitoids in these fields, comprising 74% of collected specimens. Overall, the composition of parasitoid communities is likely more sensitive to individual farm management practices or landscape composition and configuration, rather than to the type of bordering non-crop habitat. Further research is needed to determine which of these farm-level drivers are influencing parasitoid communities.