Using high-throughput amplicon sequencing to determine diet of generalist Lady Beetles in agricultural landscapes

Authors: KIM, TANIA - Kansas State University; BUKHMAN, YURY - Morgridge Institute For Research; JUSINO, MICHELLE - College Of William & Mary; Scully, Erin; SPIESMAN, BRIAN - Kansas State University; GRATTON, CLAUDIO - University Of Wisconsin

Submitted to: Biological Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/6/2022
Publication Date: 7/1/2022
Citation: Kim, T.N., Bukhman, Y.V., Jusino, M.A., Scully, E.D., Spiesman, B.J., Gratton, C. 2022. Using high-throughput amplicon sequencing to determine diet of generalist Lady Beetles in agricultural landscapes. Biological Control. 170. https://doi.org/10.1016/j.biocontrol.2022.104920.
DOI: https://doi.org/10.1016/j.biocontrol.2022.104920

Interpretive Summary: Lady beetles are general predators that feed on a variety of other insect species, several of which are prominent pests of high-value crops of agricultural importance, including maize and soybean. For this reason, lady beetles are often used to control insect pest populations in different agricultural landscapes to reduce yield losses from insect damage and the application of insecticides to control these pests. Although their ability to feed on a range of insect pests has been confirmed in lab studies, it is not currently known how many of these insects they actually feed on in the field and how their diet changes in different agricultural habitats. For example, it is presumed that landscapes containing a diverse mixture of plants will harbor a greater number of different insect species, thus increasing the dietary breadth of lady beetle predators whereas landscapes containing single crops grown in monoculture will harbor a lower diversity of insect species resulting in a lower dietary breadth. In addition, it is unknown how the diet of lady beetles changes across different cropping systems (e.g., soybean, switchgrass, and corn). In this study, we used DNA sequencing to characterize the types of insect DNA present in lady beetle guts from insects collected from monocultures of soybean, corn, and switchgrass as well as tallgrass prairies and urban habitats. The lowest diet diversity was observed in urban habitats followed by maize and lady beetles were also more likely to feed on other species of lady beetles these habitats. Significantly higher dietary breadth was observed in landscapes consisting of soybean and switchgrass monocultures and the highest dietary breadth was observed in prairie landscapes. In addition, lady beetles were more likely to feed on pest insects in habitats with higher dietary breadth, including aphids, potentially increasing their efficacy as biocontrol agents in these settings. These findings provide evidence supporting the hypothesis that dietary diversity is highest in more diverse agricultural landscapes and that the efficacy of lady beetles as biocontrol agents may vary in different cropping systems. This along with further studies will lead to the development of tools that will allow growers to make more informed decisions about which predators could be deployed in different cropping systems to effectively manage pest populations.

Technical Abstract: Understanding feeding relationships is central to understanding biological control potential in the field. However, methods to differentiate actual (or realized) feeding relationships from potential feeding relationships is lacking especially for small, generalist predators such as lady beetles. In this study, we used DNA metabarcoding approaches to characterize feeding relationships of lady beetles (Coccinellidae) in the field and validated our methods with a lab study. We first asked whether high-throughput amplicon sequencing (HTS) can characterize diets of lady beetles ranging from monotypic diets to diverse diet mixtures. We then examined whether diet composition and breadth of lady beetles collected from different habitat types in southern WI varied between monocultures of soybean and corn, diverse tallgrass prairie, and urban habitats. In our lab study where lady beetles were fed known prey items in monotypic and diverse diets, we found that HTS can accurately assess diet composition and diet breadth. In our field study, HTS documented lower prey richness and diet breadth in corn compared to soybean and grassland. We also found that reduced diet diversity was associated with an increased prevalence of intraguild predation, but that habitat and prey diversity are not necessarily correlated. We found in both the lab and field studies, that many consumer individuals would need to be assayed to fully assess diet diversity, especially in diverse systems. This information can be used to explain why biocontrol potential varies across habitat types, even with the same lady beetle communities.