Carabid beetle ecosystem services

Trophic interactions between species in agroecosystems provide key regulation ecosystem services, such as pest control and pollination, and therefore also determine the dynamics, robustness and resilience of service provision. Two ecosystem services, important in many agroecosystems, are predation on weed seeds and slugs by carabid beetles. However, two basic gaps in our knowledge limit our ability to utilise carabids in agricultural situations. First, t h e different trophic-functional groups in carabids are not yet well defined that would enable us to describe the specific associations between particular prey species. Second, the factors underlying potential switches between seed feeding and slug predation are poorly understood. Both gaps considerably limit our ability to predict for when and where weed seed and slug predation services will occur and to therefore profit from these services. In this project we address these issues within two research modules, combining field observational data, a field experiment and cutting-edge molecular approaches. The first module will unravel whether there are patterns of prey consumption consistent with robust trophic-functional groupings of carabids and prey, across a range of environmental and agricultural conditions in Austria in the three major crops, namely potato, wheat, and oilseed rape. The second module will test whether carabids switch between weed seed and slug predation and, if so, expose which factors drive the change by manipulating weed seed and slug prey availability. In doing this, we will establish whether seed and slug predation ecosystem services provided by carabids are robust, resilient and predictable, and evaluate how these two important services compete in agroecosystems. These are fundamental questions in trophic invertebrate ecology in agroecosystems. Moreover, the outcomes of this project will generate knowledge on how to achieve international goals of reducing applications of pesticides without compromising key provisioning ecosystem services such as crop yield.

Trophic interactions between species in agroecosystems provide key regulation ecosystem services, such as pest control and pollination, and therefore also determine the dynamics, robustness and resilience of service provision. Two ecosystem services, important in many agroecosystems, are predation on weed seeds and invertebrate pest by carabid beetles. However, basic gaps in our knowledge limit our ability to utilise carabids in agricultural situations. First, the different trophic-functional groups in carabids are not yet well defined that would enable us to describe the specific associations between particular prey species. Second, the factors underlying potential switches between seed feeding and pest predation are poorly understood. Both gaps considerably limit our ability to predict for when and where weed seed and slug predation services will occur and to therefore profit from these services. In this project we address these issues within two research modules, combining field observational data, experiments in the field and lab together with cutting-edge molecular approaches. We conducted surveys of feeding relationships in organically managed cereal fields as well as field and laboratory experiments. The dietary choice of ground beetles was analysed using state-of-the-art molecular methods, thus directly investigating their efficiency in biological regulation. In the first module, we identified groups within the ground beetles occurring in agricultural land on the basis of patterns of their trophic niches. The observations were done in agricultural fields along an east-west gradient from France via western to eastern Austria. In the second module, we investigated whether or to what extent food availability influences the food choice of ground beetles in a field experiment, potential seasonal changes and other factors that are driving trophic switches. Distinct trophic guilds within ground beetles were identified across the geographic gradient. Similarly, the food webs of ground beetles are shown to be influenced by the availability of food sources and are also subject to seasonal change. This results in a dynamic network of interactions among ground beetles, weed seeds, pests, and alternative prey. The present study contributes to a better understanding of the complex relationships among ground beetles, weeds and animal prey. The high detection rate for plant DNA highlights the importance of weed seeds in the diet of ground beetles and thus their importance in weed regulation. The present results indicate that this role of ground beetles has been previously underestimated. This new knowledge is particularly important with respect to the development of sustainable agricultural practices.