Author's personal copy Arthropod-Plant Interactions DOI 10.1007/s11829-015-9376-x ORIGINAL PAPER Enhancing grasshopper (Orthoptera: Acrididae) communities in sown margin strips: the role of plant diversity and identity 1,2,3 1,2,3 4 5 6 I. Badenhausser • N. Gross • S. Cordeau • L. Bruneteau • M. Vandier Received: 12 August 2014 / Accepted: 8 April 2015 Ó Springer Science+Business Media Dordrecht 2015 Abstract Grasshoppers are important components of sown and non-sown plant species. Some grasshopper spe- grassland invertebrate communities, particularly as nutrient cies were positively correlated with the abundance of grass recyclers and as prey for many bird species. Sown margin and especially of a single sown plant species, F. rubra.In strips are key features of agri-environmental schemes in contrast, other grasshopper species benefited from high European agricultural landscapes and have been shown to plant diversity likely due to their high degree of polyphagy. benefit grasshoppers depending on the initial sown seed At the community level, these contrasted responses were mixture. Understanding the mechanisms by which the translated into a positive linear relationship between grass sown mixture impacts grasshoppers in sown margin strips cover and grasshopper abundance and into a quadratic re- is the aim of our study. Here, we investigated plant– lationship between plant diversity and grasshopper diver- grasshopper interactions in sown margin strips and the sity or abundance. Since plant identity and diversity are respective effects of plant identity and diversity on driven by the initial sown mixture, our study suggests that grasshoppers. We surveyed plants and grasshoppers in 44 by optimizing the seed mixture, it is possible to manage sown margin strips located in Western France which were grasshopper diversity or abundance in sown margin strips. initially established with three sowing mixtures dominated, respectively, by alfalfa, Festuca rubra and Lolium perenne Keywords Agri-environmental schemes Á Field margin Á and Festuca arundinacea. Grasshopper species contrasted Grasshopper Á Grassland Á Biodiversity Á Farmland Á Plant– in their response to plant diversity and to the abundance of herbivore interaction Handling Editor: Heikki Hokkanen. Introduction & I. Badenhausser Agricultural intensification is currently considered as a [email protected] major driver of large-scale declines in plants, vertebrates 1 UMR7372, Station d’Ecologie de Chize´-La Rochelle, and invertebrates in Europe (Robinson and Sutherland CNRS–Universite´ de La Rochelle, Villiers en Bois, 2002). Declines in the diversity and abundance of grassland 79360 Beauvoir sur Niort, France invertebrates have been attributed to the substitution of 2 USC1339, Centre d’Etudes Biologiques de Chize´, INRA, natural habitats for arable fields or improved grasslands to Villiers en Bois, 79360 Beauvoir sur Niort, France insure maximum yield of forage (Barker 2004). Intensified 3 LTER, ZA Plaine & Val de Se`vre, CNRS, grassland management has resulted in the simplification 79360 Villiers en Bois, France and homogenization of grassland swards which are gen- 4 UMR1347 Agroe´cologie, INRA, 17, rue Sully, BP 86510, erally floristically species poor and structurally uniform 21065 Dijon Cedex, France (Vickery et al. 2001) and explain their low conservation 5 FERLUS, INRA, Les Verrines, 86600 Lusignan, France value for invertebrates (Di Giulio et al. 2001). Adding 6 URP3F, INRA, Le Cheˆne, RD150, CS 80006, grasslands with high ecological values in agricultural 86600 Lusignan, France landscape may help to support invertebrate communities 123 Author's personal copy I. Badenhausser et al. and their predators in farmlands (Woodcock et al. 2013). In Grass constitutes a prime source of food for many Euro- this context, field margins represent an interesting oppor- pean grasshopper species in grassland habitats (Bernays tunity as these habitats do not compete for space with and Chapman 1970), but beneficial effects of multiple agricultural production. foods including legumes and forbs have been shown even In Europe, sown margin strips have been a key feature for grass specialists (Unsicker et al. 2008). As a conse- of agri-environmental measures (Frampton and Dorne quence, plant diversity in sown margin strips may be a 2007). Positive impacts of sown margin strips on inverte- driver of grasshopper abundance and diversity. However, brate biodiversity were reported on butterflies (Delattre the relative importance of plant diversity versus plant et al. 2010), bees, Orthoptera and lycosid spiders (Marshall identity in explaining the relationships between plant and et al. 2006) due to the direct effects of their extensive grasshopper diversity remains unknown. This question is management (Meek et al. 2002; Cole et al. 2012; Wood- particularly relevant in the context of highly disturbed cock et al. 2009). Furthermore, some studies (e.g., Asteraki landscapes where other factors, such as dispersal, may be et al. 2004; Woodcock et al. 2009; Ernoult et al. 2013) have prime determinants of arthropod community dynamics suggested that beneficial impact of sown margin strips was (Tscharntke and Brandl 2004). mediated by the identity of the sown plant species and the In this paper, we investigated how plant communities in diversity of weed species settled through time. sown grass margin strips may impact grasshopper com- Plant community structure is widely recognized as a munities. To do so, we tested (1) how contrasted sown seed driving factor of arthropod communities in grassland mixtures used to establish margin strips impacted the habitats (Schaffers et al. 2008; Woodcock et al. 2009; composition and diversity of the plant community, and (2) Ernoult et al. 2013). Highly diverse plant communities are how the identity of the sown species as well as plant di- structurally complex and offer spatially and temporally versity impacted the abundance and species richness of more feeding and habitat niches for arthropods (Schaffers grasshoppers. We tested the following predictions: (1) et al. 2008; Dinnage et al. 2012), resulting in higher Species-rich plant communities have a positive impact on arthropod diversity and abundance (Otway et al. 2005). grasshopper species richness and abundance; (2) plant However, the effect of plant species diversity on arthropods species identity affects grasshopper abundance. is difficult to separate from the effect of one particular Specifically, grass species may have a major impact on plant species or functional group of plants (Rzanny and grasshopper abundance through their effect on the domi- Voigt 2012). Higher plant diversity may increase the nant grass-feeding guild; (3) effects of plant diversity and probability of having a plant species that favors a particular identity may be related to grasshopper species identity, arthropod species (i.e., similar to the sampling effect in according to their degree of polyphagy. Huston 1997). Also, higher plant diversity may have direct benefits for arthropod herbivore species which need to achieve a diverse diet for nutrient regulation (Unsicker Materials and methods et al. 2008; Scherber et al. 2010). Grasshoppers are important components of temperate The study area (46.11°N, 0.28°W) was an area of about grasslands (Baldi and Kisbenedek 1997). They have a 450 km2 in Western France and contained over 18,000 considerable functional importance as primary consumers, fields of intensive agriculture, mostly dedicated to cereal nutrient recyclers (Belovsky and Slade 2000) and prey for a crop production. Grasslands represented about 10 % of the wide range of taxa such as birds (Barker 2004). Conse- total surface. A total of 44 5-m wide sown margin strips quently, conservation strategies of farmland bird species were selected over the study area. The same sown margin include specific agri-environmental schemes to enhance strips were sampled over a 2-year period (2008 and 2009). grasshopper abundances in grasslands (Bretagnolle et al. Three types of seed mixtures were sown by farmers in 2011). Although precise data are lacking, grasshoppers are the margin strips: GL (n = 4), grass-legume mixtures currently thought to decline in farmlands, as a consequence dominated by Medicago sativa L. ([75 % of the total seed of agricultural intensification and decrease in grassland weight), associated with Lolium perenne L. or Festuca cover at the landscape scale (Barker 2004). In this context, pratense Huds. in lower rates (\25 %); GFrLp (n = 20), sown margin strips have been demonstrated to enhance grass mixtures dominated by L. perenne ([58 %) and grasshopper abundances (Marshall et al. 2006; Baden- Festuca rubra L. (40 %), sometimes associated with Tri- hausser and Cordeau 2012) depending on the sowing folium repens L. (\2 %); and GFa (n = 20), grass mixtures mixture used to establish the margin strips (Badenhausser dominated by Festuca arundinacea Scherb. (either [72 % and Cordeau 2012). Badenhausser and Cordeau (2012) if associated with others grasses or 100 % in pure-stand). showed that seed mixture dominated by alfalfa had low Other species were sown in lower proportion, i.e., T. repens value for grasshoppers compared with grass mixtures. (2 %), Dactylis glomerata L. (10 %) and F. pratense 123 Author's personal copy Enhancing grasshopper (Orthoptera: Acrididae) communities in sown margin strips: the role of… (15 %). Most of the margin strips were established in 2005 random effects to account for the repeated measures for the or 2006