Landscape configuration affects herbivore–parasitoid communities in oilseed rape

Journal of Pest Science, Feb 2018

It is crucial to consider the effects of large-scale drivers on species presences and ecological interactions to understand what structures communities. In our study, we investigated how the species composition and the potential interaction networks of herbivore and parasitoid communities in oilseed rape fields are affected by agricultural landscape characteristics. Insect communities of 26 winter oilseed rape fields in southern Sweden were captured in water traps over a continuous time span of 30 ± 2 days. In total, 31% of the variation in the composition of herbivore host communities was explained by a combination of the surrounding oilseed rape area in the study year and the previous year and distance to the nearest forest. The oilseed rape area in the study year and distance to forest also explained 14% of the variation in the composition of parasitoid communities. Distance to the nearest forest together with the area of oilseed rape in the previous year explained 45% of the variation in asymmetry of interaction webs. These results indicate that several measures of landscape configuration are important both for the composition of host and parasitoid communities and also for the structure of interaction networks. Our results support the view that it is an appropriate strategy to cultivate oilseed rape in landscapes that are far away from forests, in order to minimize recolonization by pest species and at the same time to attract parasitoid species from the open landscape.

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Landscape configuration affects herbivore–parasitoid communities in oilseed rape

Journal of Pest Science https://doi.org/10.1007/s10340 Landscape configuration affects herbivore-parasitoid communities in oilseed rape Josef S. Berger 0 1 2 Klaus Birkhofer 0 1 2 Helena I. Hanson 0 1 2 Katarina Hedlund 0 1 2 0 Department of Ecology, Brandenburg University of Technology Cottbus-Senftenberg , Konrad-Wachsmann-Allee 6, 03046 Cottbus , Germany 1 Centre for Environmental and Climate Research, Lund University , Sölvegatan 37, 223 62 Lund , Sweden 2 Department of Biology, Lund University , Sölvegatan 37, 223 62 Lund , Sweden 3 Josef S. Berger It is crucial to consider the effects of large-scale drivers on species presences and ecological interactions to understand what structures communities. In our study, we investigated how the species composition and the potential interaction networks of herbivore and parasitoid communities in oilseed rape fields are affected by agricultural landscape characteristics. Insect communities of 26 winter oilseed rape fields in southern Sweden were captured in water traps over a continuous time span of 30 ± 2 days. In total, 31% of the variation in the composition of herbivore host communities was explained by a combination of the surrounding oilseed rape area in the study year and the previous year and distance to the nearest forest. The oilseed rape area in the study year and distance to forest also explained 14% of the variation in the composition of parasitoid communities. Distance to the nearest forest together with the area of oilseed rape in the previous year explained 45% of the variation in asymmetry of interaction webs. These results indicate that several measures of landscape configuration are important both for the composition of host and parasitoid communities and also for the structure of interaction networks. Our results support the view that it is an appropriate strategy to cultivate oilseed rape in landscapes that are far away from forests, in order to minimize recolonization by pest species and at the same time to attract parasitoid species from the open landscape. Landscape configuration; Community composition; Web asymmetry; Herbivore community; Parasitoid community; Oilseed rape Key messages Landscape effects on parasitoids of oilseed rape pests have hitherto mainly been studied on a few species. Communicated by S. Macfadyen. • We tested the hypotheses that several landscape variables affect the species composition of both parasitoid and host communities and their interactions. Distance from the site to forested land, and oilseed rape area within a 1 km radius, was important predictor of variation in community composition of both trophic levels. Host–parasitoid interaction networks become more asymmetric with increasing distance from forests due to relatively fewer pest than parasitoid species. Consequently, we predict that growing oilseed rape farther away from forests will attract fewer host species and more species of their natural enemies. Introduction Oilseed rape (OSR) is a suitable habitat for many herbivorous insect species of which some cause considerable economic losses, while others are of little or no economic importance (Alford et al. 2003) . In Europe, herbivores in OSR are attacked by at least 80 species of parasitoid Hymenoptera, while only 12 of them are considered to be economically important as biological control agents (Ulber et al. 2010) . In intensively managed agricultural landscapes, the presence of hosts and their parasitoids may depend on management strategies and landscape characteristics. Previous research in OSR habitats has mostly focused on single or few target species with high economic impact, such as the rape pollen beetle Brassicogethes aeneus and its parasitoids (Thies and Tscharntke 2010; Rusch et al. 2011, 2013; Schneider et al. 2015) . However, despite the presence of a diverse herbivore (Hiiesaar et al. 2003; Vaitelytė et al. 2013; Metspalu et al. 2014) and parasitoid community (Tarang et al. 2004; Nerad et al. 2011) in oilseed rape, our knowledge about landscape effects on multiple species in this ecosystem is limited to a few studies (Zaller et al. 2008, 2009; Frank et al. 2010) . To fully understand processes that structure these invertebrate communities, we need to take into account not only traditional components of biodiversity such as the total number of species, but also species identity and community composition (Symstad et al. 1998; Emery and Gross 2007) and the ecological interactions between these species (Tylianakis et al. 2010; Miranda et al. 2013) . Landscape characteristics influence invertebrate communities in agricultural crops in various ways (Tscharntke et al. 2007) . Landscape complexity for example enhances species richness, abundance or fecundity of parasitoids (Bianchi et al. 2006; Rusch et al. 2010) . Parasitoids of the rape pollen beetle also have higher parasitism rates in structurally complex as opposed to structurally simple landscapes (Thie (...truncated)


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Josef S. Berger, Klaus Birkhofer, Helena I. Hanson, Katarina Hedlund. Landscape configuration affects herbivore–parasitoid communities in oilseed rape, Journal of Pest Science, 2018, pp. 1-13, DOI: 10.1007/s10340-018-0965-1