Edges in Agricultural Landscapes: Species Interactions and Movement of Natural Enemies

Abstract

Agricultural landscapes can be characterized as a mosaic of habitat patches interspersed with hostile matrix, or as a gradient of patches ranging from suitable to unsuitable for different species. Arthropods moving through these landscapes encounter a range of edges, with different permeability. Patches of native vegetation in these landscapes may support natural enemies of crop pests by providing alternate hosts for parasitic wasps and/or acting as a source for predatory insects. We test this by quantifying species interactions and measuring movement across different edge-types. A high diversity of parasitoid species used hosts in the native vegetation patches, however we recorded few instances of the same parasitoid species using hosts in both the native vegetation and the crop (canola). However, we did find overall greater densities of parasitoids moving from native vegetation into the crop. Of the parasitoid groups examined, parasitoids of aphids (Braconidae: Aphidiinae) frequently moved from native vegetation into canola. In contrast, parasitoids of caterpillars (Braconidae: Microgastrinae) moved commonly from cereal fields into canola. Late season samples showed both aphids and parasitoids moving frequently out of native vegetation, in contrast predators moved less commonly from native vegetation (across the whole season). The season-long net advantage or disadvantage of native vegetation for pest control services is therefore difficult to evaluate. It appears that the different edge-types alter movement patterns of natural enemies more so than herbivorous pest species, and this may impact pest control services.

Effects of landscape configuration on mapping ecosystem service capacity: a review of evidence and a case study in Scotland

“…Second, ES capacity is affected by the use and structure of multiple patches (e.g., Bodin et al 2006;Ludwig et al 2007;Liu et al 2012;Bateni et al 2013), such as foraging behaviour or nutrient flows through a landscape. Third, ES capacity is affected by the structure of a single patch, such as patch size or edge effects (e.g., Forman 1995;Macfadyen and Muller 2013). Fourth, ES capacity is affected by the presence of linear elements, such as hedgerows and grass margins (e.g., Falloon et al 2004;Pollard and Holland 2006;Borin et al 2010).…”

Towards a landscape scale management of pesticides: ERA using changes in modelled occupancy and abundance to assess long-term population impacts of pesticides

“…For example, in Holland, Aegerter et al (2007) have shown that regular geometry of landscape construction results in bias in simulation results. In fact species can utilise resources from both crop and non-crop patches, and the decision to move from one place to another is made depending on the risks associated with a particular landscape-matrix type (Macfadeyen and Muller 2013). This phenomenon makes prediction even more complicated.…”

Non‐random food‐web assembly at habitat edges increases connectivity and functional redundancy

“…Although there is widespread evidence for the spillover of prey and consumers between adjacent ecosystems (Rand et al 2006;Vacher et al 2008;Johnson et al 2011;Macfadyen and Muller 2013), the implications of this for species interactions have not previously been addressed beyond simple…”

“…These habitat edges can influence patterns of species abundance, distribution and diversity (Dyer and Landis 1997;Ewers and Didham 2008;Murphy et al 2016), alter dispersal processes (Duelli et al 1990;Macfadyen and Muller 2013) and even interactions among species (Fagan et al 1999;Ries et al 2004;). Species interactions underpin many important ecosystem functions and services (Klein et al 2003;Macfadyen et al 2011), and they are frequently altered by changes in the…”