Complex landscapes, complex diets: DNA metabarcoding reveals lady beetle prey richness increases with landcover diversity

Understanding the capacity of mobile organisms such as insects to utilize resources across different patches in a landscape can reveal strategies for their conservation. Past research suggests that higher levels of non-crop habitat or landcover diversity in agricultural regions typically benefit generalist predators who can fortify their diets with prey from multiple adjacent habitats. For some taxa such as lady beetles (Coccinellidae), dietary diversity is associated with improved fitness, but foraging patterns in real landscapes are hard to measure. We used a DNA metabarcoding approach to explore how the presence and taxonomic richness of arthropod prey in lady beetle diets varied by local habitat (crop vs. non-crop) and landscape complexity (non-crop habitat and landcover diversity in a 250 m radius). We collected over 500 individual lady beetles from a range of landscapes in 2019 and 2021 in southern Wisconsin (USA), performed whole-body DNA extractions, amplified arthropod DNA using primers optimized for insectivore diets, and used Illumina sequencing to characterize the taxonomic composition and diversity of prey. We found 50 unique prey taxa in lady beetle guts from eight arthropod orders (mostly flies, true bugs, and thrips). Lady beetles in landscapes with a greater proportion of crops were slightly more likely to have prey in their gut, and community-level prey richness was strongly positively correlated with surrounding landcover diversity. This effect was dampened slightly in high-crop landscapes, likely due to a smaller prey species pool available to predators. Our results enhance knowledge of lady beetle trophic ecology and demonstrate that supplementation of diets through increased habitat diversity may be an important mechanism for the success of mobile generalists in complex landscapes.