Trait-based characterisation of parasitoid wasp communities in natural and agricultural areas

Life-history traits are increasingly used to understand how arthropod communities assemble and function under diverse conditions, for example why some species are better adapted to agricultural intensification than others. We aimed to understand which traits characterise parasitoid wasps under agricultural disturbances. To this end, we studied parasitoid communities from pomegranate orchards and nearby natural habitats in Israel. Ten sites along a climate gradient were sampled thrice along one fruit-growing season. We compiled information on life-history traits associated with development, adult diet and host taxa, for 27 well-represented parasitoid species. We tested for relationships between the parasitoids' abundances, functional traits and environmental conditions, using RLQ and fourth-corner analyses. Life-history traits were highly related to environmental variables. Koinobionts (wasps whose parasitized hosts feed and grow), and parasitoids of aphids and whiteflies, were more common, and sugar-feeding was less common, in orchards than in natural habitats. Parasitism of larval hosts correlated with aridity, while egg parasitism increased with herbaceous vegetation cover. Host composition and koinobiosis shape parasitoid communities in the orchards. Koinobiosis is often associated with life-history traits such as small eggs, short life-span, early egg maturation and high fecundity, which may be adaptive in the frequently disturbed orchard habitats. Further, dense vegetation conditions seem to favour egg parasitism (perhaps because of reduced risks of egg desication), while larval parasitism is more common in arid seasons and sites. These findings provide initial insights regarding the effects of land use and climate on the functional characteristics of parasitoid communities.