The role of parasitoids in the integration and structuring of thophic networks

Abstract

Most of the global biodiversity of insects is composed of complex networks of tri-trophic interactions formed by parasitoids, their herbivorous hosts, and the plants on which they live and feed. In recent years, there has been a high increase in the taxa of extinction and invasion of ecosystems, in such a way that we are losing species that we did not even know about. In this way, studies of communities, especially involving the description of the species and their interactions, contribute to a better understanding of the causes and consequences that the loss or addition of a species can cause for all ecosystems. In particular, understanding the interactions of host-parasitoids can carry knowledge of practical use in the biological control of insects and the reduction of the use of agrochemicals. In the first article, we characterized communities of herbivorous insects and their parasitoids associated with three species of Fabaceae: Senna multijulga, Inga vera, and Leucaena leucocephala, with 5,353 individuals and 77 species. We found that the Hymenoptera order, a group dominated by parasitoid wasps, was more diverse in all systems studied (n = 48). Furthermore, the insect communities associated with these plants seem to be highly specific to their hosts (plant and herbivore hosts), as only four (three parasitoids and one herbivore) species connect different plants. We discovered that the number of seeds promoted a trophic cascade on the abundance and richness of herbivores and parasitoids as well as the most abundant insect groups on the abundance and richness of parasitoids. In the second article, we described the trophic network of L. leucocephala, and we relate the quantitative metrics, the pattern of predation, and oviposition behavior of Acantoscelides macrophthalmus to the size of the resource. The results of the article show a community of 17 species, composed of 6 herbivores, 9 parasitoids, and 1 hyperparasitoid. The seed biomass trait showed a strong influence on the insects and the complexity of the food web. We observed that fruits with heavier seeds have greater abundance, richness, connectivity, and number of interactions. Furthermore, A. macrophthalmus laid more eggs in fruits with heavier seeds. In general, seeds predated by Coleoptera, mainly represented by A. macrophthalmus, were four times heavier than seeds from other categories, including those not predated. Finally, our study emphasizes the importance of including parasitoids in community research because they are very diverse and have an important role in ecosystem services.