Aerial invertebrate functional groups respond to landscape composition with only detritivores and predators responding to agri-environment scheme management

Abstract

Landscape-scale agricultural intensification is a major driver of biodiversity loss. Highly mobile species, such as aerial invertebrates may be disproportionately affected by land cover at large spatial scales due to their ability to disperse. Assessing the efficacy of environmentally friendly farming, such as Agri-Environment Schemes (AES), therefore, requires establishing the influence of land cover beyond focal farms or fields, contextualising the impact of agricultural management. This study measured the response of aerial invertebrate functional groups to AES management in improved and semi-improved upland grasslands accounting for spatial autocorrelation and multi-scale effects of land cover within buffers varying from 100 m to 5 km at 88 paired fields. Total aerial invertebrate abundance and diversity, including detritivores, herbivores, nectivores, predators and parasitoids all responded to different land cover types at varying scales indicative of highly complex and idiosyncratic functional group responses to landscape.After accounting for spatial autocorrelation and multi-scale landscape composition, total aerial invertebrate abundance was unaffected by agricultural management but diversity was (5%) higher in AES than conventionally managed fields. Detritivore (mostly Mycetophilidae fungus gnat) diversity and abundance were higher in AES than conventional fields, but only on improved grasslands, while predator (adult Muscidae house fly, Scathophagidae dung fly and Dolichopodidae long-legged fly) diversity was lower but abundance higher in AES than conventional fields. Aerial invertebrate herbivores (Anthomyiidae root-maggot flies and Cecidomyiidae gall midges and gnats), nectivores (Syrphidae hoverflies and Apoidea bees) and parasitoids (Ichneumonidae wasps) responded to landscape composition, but not agricultural management. Synthesis and Applications: this study suggests that landscape composition drives aerial invertebrate functional group diversity and abundance at multiple spatial scales. Nevertheless, the responses of some functional groups (detritivores and predators) to local agricultural management suggest that AES management may contribute to the maintenance or enhancement of ecosystem service delivery (nutrient cycling and pest biocontrol). Explicitly accounting for multi-scale landscape effects is necessary when assessing the impact of agricultural management on highly mobile taxa.