Biodiversity and trophic interactions in agricultural mosaic landscapes, comparing bees, wasps and their natural enemies

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Global biodiversity is declining at an alarming rate and traditional conservation areas are no longer sufficient to slow this decline, so the potential contribution of managed land for conservation is increasingly acknowledged. This includes a broadening of the perspective from the field and farm to the landscape level, considering the often neglected spatial and temporal turnover in anthropogenic mosaic landscapes. Here we will use a highly replicated study design with the experimental exposure of standardized nesting resources to examine the relative importance of habitat type to landscape diversity using trap-nesting bees, wasps and their natural enemies. We will analyze the scale-dependence of partitioned biodiversity and quantify host-parasitoid and prey-predator interactions, as well as make food web statistics with a fully quantified interaction web (following Tylianakis et al. 2007, Nature 445: 2002-5). We will show how the major habitat types in our mosaic landscapes (and different years) contribute to overall species richness, comparing wheat, oilseed rape, grassland, field margin strips, fallows and forest margins, which represent a gradient of anthropogenic disturbance. We will examine how landscape composition influences the relative contribution of the six habitat types to species richness by focusing on a gradient of simple to complex structured landscapes. Further, we expect enemy richness to be related to host/prey mortality, so we will contribute to this highly debated topic. The mosaic structure of agricultural landscapes allow to study little known effects of landscape configuration, including spillover effects across habitats, inhibition of dispersal (by hostile cereal fields) and facilitation (by grassy corridors). Experiments with marked bee and wasp individuals allow to describe foraging behaviour and resource use across habitats.