Enhancing floral diversity to increase the robustness of grassland beetle assemblages to environmental change

Intensive grassland management has produced floristically species poor swards supporting a limited invertebrate fauna. Low cost seed mixtures can be used to increase floristic diversity and so diversify the food resource of phytophagous invertebrate. We quantify trophic links between plants and phytophagous beetles in grasslands established using three seed mixtures. Using food webs, we model secondary extinctions from the beetle communities caused by the loss of host-plants. Plant species were eliminated according to three scenarios: (1) drought intolerant first; (2) low nutrient status first; (3) stress tolerant first. Diverse seed mixtures containing grasses, legumes, and nonlegume forbs, were more robust to secondary beetle extinctions. The highest diversity seed mixture increased robustness under scenarios of extreme drought in three out of four tested management regimes. Simple and low cost seed mixtures have the potential to promote landscape scale robustness to future environmental change for native invertebrates.