Local and broadscale landscape structure differentially impact predation of two potato pests.

Agricultural habitats are the recipients of ecosystem services provided by mobile arthropods like pollinators and natural enemies. These organisms can disperse between non-crop habitats and crops and can benefit from resources in non-crop areas. Thus, it may be important to conserve non-crop habitats to maintain ecosystem services within crops. However, even single ecosystem services, such as pollination or predation of pests, may be provided by a complex of species. Different species may respond to landscape structure at differing spatial scales. This raises the question: What scales should conservation take place at to sustain an ecosystem service? Here, we examine variation in predation of two potato pests in response to landscape structure. Specifically, predation of Colorado potato beetle, Leptinotarsa decemlineata, and green peach aphid, Myzus persicae, were quantified in potato and field-margin habitats set in landscapes that varied at different scales. At a local scale (meters), potato fields of different sizes were bordered by different areas of grassy field margin. At a broad scale (kilometers), these habitats were set in landscapes composed of varying percentages of non-crop habitat. Predation of both pests was associated with landscape structure, but this relationship occurred at different scales for each pest and interacted differently with habitat type. Predation of L. decemlineata eggs was greater in field margins than in the potato crop and increased in both habitats when field margins were large relative to potatoes. In contrast, aphid predation in field margins increased with the area of non-crop habitat within 1.5 km, but did not change in adjacent potato. These data emphasize that, even a single ecosystem service, such as predation of pests, can be influenced by landscape structure at multiple scales. More generally, it may be necessary to conserve heterogeneity both at local scales (individual farm fields) and broad scales (entire mosaic landscapes) to maintain ecosystem services. This may be especially true for ecosystem services that are the aggregate result of the actions of many species or ecological processes.