Landscape composition influences invertebrate herbivory on flowering forbs in semi-natural grasslands

Landscape-scale land use is important in driving species communities and interactions. However, despite increasing concerns regarding the ecological consequences of insect declines, our understanding of how the relative proportions of different land cover types influence insect herbivory in species-rich semi-natural habitats remains limited. This study assessed leaf, stem, and flower herbivory across 47 flowering forb species in 18 semi-natural grassland sites in southern Sweden, where the surrounding landscape composition was quantified by the proportions of arable crops, forests, leys, and permanent grasslands. In addition to landscape effects, we examined the mediating roles of plant traits, plant diversity, and community composition to better understand how land use affects herbivory. Proportion of permanent grasslands and arable crops had the strongest influence on herbivory. The occurrence probabilities of leaf and stem herbivory increased as the proportion of permanent grasslands increased and the proportion of arable crops decreased. For herbivory intensity, leaf chewing damage exhibited the most significant response, following a trend similar to herbivory occurrence, while flower damage intensity increased with proportion of permanent grasslands but decreased with proportion of forest. These effects were less consistent at the species level, with varying magnitudes and directions of response. Plant community composition and traits, such as plant height and Specific Leaf Area (SLA), mediated landscape composition effects on leaf chewing herbivory, such that the proportion of arable crops were linked to higher SLA and taller plants, which in turn promoted leaf chewing herbivory. Our findings highlight the importance of preserving permanent grasslands at the landscape scale for maintaining insect herbivory levels on flowering forbs in local semi-natural grasslands, and call for the need to better understand the ecosystem consequences of reduced herbivory in agricultural landscapes.