Research trends in ecosystem services provided by insects.

Insects play akeyrole in the regulation and dynamics of many ecosystem services (ES). However, this role is often assumed, withlimited or no experimental quantification of itsreal value.We examine publication trends in the research on ES provided by insects, ascertainingwhich ESand taxa were more intensivelyinvestigated,and with which methodological approaches,with particular emphasison experimental approaches. We performed a systematicliterature search to identify which EShave been attributed to insects. Thenweclassifiedthereferences retrieved according to theES, taxonomic group and ecosystem studied, as well as to the method applied to quantify the ES(in four categories:no quantification, proxies, direct quantificationand experiments). Pollination, biological control, food provisioning and recycling organic matter are the most studied ES. However, the majority of papers do not specify theES under consideration, and from those that do it, most do not quantifythe ESprovided. From the rest, alarge number of publications use proxies as indicators for ES, assuming or inferringtheir provision through indirect measurementssuch as species abundances, species richness, diversity indices, species density or the number of functional groups. Pollinators, predators, parasitoids, herbivores and decomposers are the most studied functional groups, while Hymenoptera, Coleoptera andDiptera arethe most studiedtaxa. Experimental studies are relatively scarceandthey mainly focus onbiological control, pollination,and decompositionperformed in agroecosystems. These results suggest that our current knowledge on the ES provided by insects is relatively scarce andbiased, and showsobvious gaps in the least-studied functional and taxonomic groups. An ambitious research agenda to improve the empirical and experimental evidence of the role played byinsects in ES provision is essential to fully assess synergies between functional ecology and biodiversity conservatio