Parasitoid diversity and parasitism rates in Pampean agricultural mosaics are enhanced by landscape heterogeneity

Abstract

Agricultural intensification affects negatively on landscape heterogeneity, biodiversity, biotic interactions and the associated ecological functions. Here, we describe the structure of herbivore–parasitoid interactions by analysing the rates of parasitism and their variability in relation to landscape heterogeneity. Phytometer traps (Commelina erecta L.) infested with a specific leaf miner fly (Liriomyza commelinae Walker) were used to analyse whether landscape heterogeneity influences the parasitism rates and the associated parasitoid diversity. For that reason, phytometers were distributed in 21 sampling sites along rural roads. Not only did landscape heterogeneity influence positively on parasitoid species richness at the site level (local scale), but it also influenced on the percentage of total parasitism and specific parasitism rates of several species. Although the parasitoid diversity was similar at the landscape scale, the evenness of interactions changed substantially among sites. Possibly, the richer plant communities in heterogeneous landscapes provide with a wider combination of resources for parasitoids. The increase in both parasitoid species richness and biological regulation supports the adoption of management strategies that creates heterogeneous farmland mosaics. Landscape heterogeneity may be enhanced by diversifying crop sequences and sowing wildflower strips along field margins. Thus, non-crop habitats could serve as reservoirs for generalist parasitoids of novel pest species, supplying biological regulation services in agricultural landscapes. We argue that enhancing agrobiodiversity is a key goal to design agroecosystems that ensure food security, equity and sustainability.