A network approach reveals parasitoid wasps to be generalized nectar foragers

Abstract

Despite many efforts to sustain parasitoid populations in agroecosystems to help control pests, relatively little is known about parasitoid-flower interactions and how dependent each partner is on the other. There are few comprehensive, species-specific, community-level observations of parasitoid-flower interactions. Observing flower visitation by parasitoid species is challenging because most parasitoids are small and visit flowers infrequently. Further, the extreme diversity of parasitoids poses challenges for identification, and only a few experts can identify parasitoids to species. To explore the potential for a flower-visitor network approach to improve our understanding of parasitoid foraging ecology, we utilized published and publicly available flower-visitor datasets from the Interaction Web Database. Parasitoid species were present in almost half of the flower-visitor datasets in the Interaction Web Database but constituted a very small proportion of all flower visiting species. We analyzed the only parasitoid-flower subnetwork that was both speciose and documented heterogeneity in the number of flowering plant species visited by parasitoids. On average, parasitoids were more generalized in flower visitation than predicted under null expectations, given their prevalence in the network. Further, many individual flower and parasitoid species might be more generalized than they appeared as evidenced by a specialization metric less biased by sampling effects. These plant and parasitoid species might therefore be more useful for conservation biological control efforts than initially expected. Finally, the nested structure of the network indicates the potential for a subset of the flower community to support generalized, and any potential specialized, parasitoid nectar foragers in the field.