Enhancing grasshopper (Orthoptera: Acrididae) communities in sown margin strips: the role of plant diversity and identity

Grasshoppers are important components of grassland invertebrate communities, particularly as nutrient recyclers and as prey for many bird species. Sown margin strips are key features of agri-environmental schemes in European agricultural landscapes and have been shown to benefit grasshoppers depending on the initial sown seed mixture. Understanding the mechanisms by which the sown mixture impacts grasshoppers in sown margin strips is the aim of our study. Here, we investigated plant–grasshopper interactions in sown margin strips and the respective effects of plant identity and diversity on grasshoppers. We surveyed plants and grasshoppers in 44 sown margin strips located in Western France which were initially established with three sowing mixtures dominated, respectively, by alfalfa, Festuca rubra and Lolium perenne and Festuca arundinacea. Grasshopper species contrasted in their response to plant diversity and to the abundance of sown and non-sown plant species. Some grasshopper species were positively correlated with the abundance of grass and especially of a single sown plant species, F. rubra. In contrast, other grasshopper species benefited from high plant diversity likely due to their high degree of polyphagy. At the community level, these contrasted responses were translated into a positive linear relationship between grass cover and grasshopper abundance and into a quadratic relationship between plant diversity and grasshopper diversity or abundance. Since plant identity and diversity are driven by the initial sown mixture, our study suggests that by optimizing the seed mixture, it is possible to manage grasshopper diversity or abundance in sown margin strips.