Unveiling the diet of predatory mites through DNA metabarcoding

Abstract: Despite the importance of predatory mites as biological control agents, the way thatgeneralist species can maintain in agrosystems, the alternative preys they can feed on, the waythey choose to eat one prey or another are poorly known. New technologies that allowdetermining the diet of predatory mites in the field are highly desirable to supporting biologicalcontrol programs. Traditional molecular methods to assess diet of predatory mites have beendeveloped, however, they just make possible identification of previously known prey. Apromising avenue for deciphering diet of predators is offered by DNA metabarcoding, whichhas been recently used for studying trophic interactions in arthropod communities inagricultural systems. However, this approach has not yet been applied to minute arthropods likemites. This first attempt of applying a metabarcoding approach to determine the diet ofpredatory mites included steps for both methodological developments and in situ evaluations.DNA extraction method that could enhance prey detection was defined. DNA mini-barcodesprimers with highest efficiency to the potential prey and low efficiency to predatory mites, thatcould increase detectability of DNA prey traces in the predatory mite body were designed andevaluated. Controlled feeding experiments were conducted and demonstrated the methodefficiency. In situ evaluations of phytoseiid mites in fruit crops unveil new predator – preyassociations for several phytoseiid mites. Shortcomings and perspectives for the innovativetechnology are discussed.