Effects of landscape complexity on the functional diversity of natural enemies and the ecosystem service of pest control

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The relationship between biodiversity and ecosystem functioning (BEF) is central to our understanding of community ecology. Ecosystem services such as pest control (i.e. ecosystem functions that benefits humans) are crucial to ensure sustainable and resilient food production systems, but there are no clear patterns on how landscape complexity (defined as proportion of natural or seminatural habitat in a focal landscape) and biodiversity affects them. Insect pests of crops cause billions of dollars of losses each year. While insecticides are effective in the short term, they are costly and negatively affect non-target species, ultimately disrupting ecosystems and reducing sustainability. Using existing natural enemies (predators and parasitoids) to provide pest control services is cost-free and can improve sustainability, but many of the underlying mechanisms by which natural enemies control pests remain poorly understood. The long-term goal of my research program is to understand interactions among plants, herbivore pests and natural enemies in agricultural landscapes, with the aim to enhance arthropod-mediated ecosystem services. Landscape complexity decreases with increased agricultural intensification, reducing natural enemy populations, but recent work found inconsistent patterns between landscape complexity and pest control, highlighting the need for a mechanistic understanding of BEF relationships at the landscape scale. Shifting the focus from taxonomic diversity to the diversity of functional traits (body size, feeding specialization, activity period, etc.) has improved our understanding BEF relationships in plant and pollinator communities, but has seldom been investigated for natural enemy communities. Over the next five years, I will train 14 students while we investigate the effects of landscape complexity on the functional diversity of natural enemies and pests in agroecosystems. We will examine how local filters (habitat identity and disturbance level) affect functional diversity by simultaneously sampling multiple habitats in focal landscapes. Using manipulative experiments, we will determine how the addition of flowering strips to field borders affects natural enemy functional diversity and pest control in crops, and how this is moderated by landscape complexity. Finally, using molecular gut content analyses, we will examine the association between levels of pest control and natural enemy functional diversity. This research will aid in determining what amount and arrangement of suitable natural enemy habitat is ideal to support functional natural enemy communities and maximize pest control in agricultural landscapes.