Seed predation intensity and stability in agro-ecosystems: Role of predator diversity and soil disturbance

Seed predation by arthropods can contribute in regulating population and community dynamics of weeds. While the role of insects, and especially ground beetles (Coleoptera: Carabidae) as seed predators in crop fields is well studied, the drivers of predation stability and the relationships between species diversity and predation are less understood. The aims of the study were: 1) to unveil the direct relationships between predator community diversity and seed predation intensity and stability, and 2) to test the effects of soil disturbance (conventional vs. conservation tillage) and distance from field margin on seed predator communities and predation. Seed predation was measured using seed cards, and predator communities were sampled using pitfall traps over two years. Granivorous ground beetles, ants and crickets were the most abundant seed predators in both conventional and conservation tillage fields. Abundant and diverse predator communities were beneficial to predation intensity and stability. However, in communities dominated by large predators, an increase in number of species was related to a partial suppression of seed predation. Soil disturbance per se did not influence the overall predator community composition and predation, but it modified their spatial patterns within the fields. At the margins of conventional tillage fields, predation was lower and patchier than at the margins of conservation tillage fields. However, predation increased more steeply towards the center of conventional tillage field. Our results could find applications in sustainable weed management through biological control, as well as in better understanding the role of functional diversity in regulating ecosystem services.