Food webs and multiple biotic interactions in plant–herbivore models

Trophic relationships between plants and insects are not confined to biological interactions such as herbivory (i.e., direct consumption of one primary producer by a predator). In an ecological approach, many other interactions, trophic or even nontrophic, may influence plant herbivory by insects. These interactions are related to the complexity and the diversity of the fauna and flora.Plants and insects own to food webs, characterized by properties emerging from the identity of organisms and from the organisation of the links they develop with each other. These organisms can be considered as both taxonomic and functional units of biodiversity highlighting the complexity of food webs. Insects can be predated (e.g., by other arthropods or birds), parasitized and competed with for resources. Plant competition and availability of resources for primary producers may also influence the relationship between plants and their consumers.The inclusion of predation mechanisms in plant–insect interactions leads to the theory of trophic cascades that advanced our understanding of the process of herbivory by insects. Ecological theories give a framework to assess the way by which these biotic interactions may be controlled in natural systems. Trophic cascades provide also biological tools for the management of agroecosystems, especially for biological control of herbivores and the promotion of biodiversity.Biological interactions within food webs may also be nontrophic and alter plant–insect herbivory. Intraguild competition, interference, abiotic resources, microclimate and changes in animal behaviour are some of the drivers which may influence plant and insects, and thus their trophic relationships