Food webs in nature have multiple, reticulate connections between a diversity of consumers and resources. Such complexity affects web dynamics: it first spreads the direct effects of consumption and productivity throughout the web rather than focusing them at particular "trophic levels." Second, consumer densities are often donor controlled with food from across the trophic spectrum, the herbivore and detrital channels, other habitats, life-history omnivory, and even trophic mutualism. Although consumers usually do not affect these resources, increased numbers often allow consumers to depress other resources to levels lower than if donor-controlled resources were absent. We propose that such donor-controlled and "multichannel" omnivory is a general feature of consumer control and central to food web dynamics. This observation is contrary to the normal practice of inferring dynamics by simplifying webs into a few linear "trophic levels," as per "green world" theories. Such theories do not accommodate commo...

Food Web Complexity and Community Dynamics

Theoretical developments are helping us to comprehend the basic parameters governing the dynamics of the interactions between generalist predators and their many pest and nonpest prey. In practice, however, inter- and intraspecific interactions between generalist predators, and between the predators and their prey, within multispecies systems under the influence of rapidly changing biotic and abiotic variables are difficult to predict. We discuss trade-offs between the relative merits of specialists and generalists that allow both to be effective, and often complementary, under different circumstances. A review of manipulative field studies showed that in approximately 75% of cases, generalist predators, whether single species or species assemblages, reduced pest numbers significantly. Techniques for manipulating predator numbers to enhance pest control at different scales are discussed. We now need to find ways of disentangling the factors influencing positive and negative interactions within natural enemy communities in order to optimize beneficial synergies leading to pest control.

Can generalist predators be effective biocontrol agents

Agroecology: the science of natural resource management for poor farmers in marginal environments

Summary
1Many insects derive nutritional advantage from persistent associations with microorganisms that variously synthesize essential nutrients or digest and detoxify ingested food. These persistent relationships are symbioses.
2There is strong experimental evidence that symbiotic microorganisms provide plant sap-feeding insects with essential amino acids and contribute to the digestion of cellulose in some wood-feeding insects, including lower termites. Basic nutritional information is, however, lacking for many associations, including the relative roles of microbial and intrinsic sources of cellulose degradation in many insects and B-vitamin provisioning by microorganisms in blood-feeding insects.
3Some nutritional interactions between insects and their symbiotic microorganisms vary among conspecifics and closely related species. This variation can, in principle, contribute to nutritional explanations for variation in the abundance and distribution of insects. For example, the plant utilization traits of phloem-feeding aphids and stinkbugs have been demonstrated to depend on the identity of microbial partners. Evidence that associations can evolve rapidly comes from the demonstration that the impact of the bacterium Wolbachia on natural populations of its insect host can change from deleterious to beneficial within two decades.
4Developing genomic tools, especially massively parallel sequencing and metagenomic analyses, offer the opportunity to explore the metabolic capabilities of symbiotic microorganisms and their insect hosts, from which defined hypotheses of nutritional function can be constructed. Nutritional ecology provides the appropriate framework to test these hypotheses in the relevant ecological context.

https://besjournals.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-2435.2008.01442.x

The microbial dimension in insect nutritional ecology

The primary reason animals, including insect herbivores, eat is to acquire a mix of nutrients needed to fuel the processes of growth, development, and reproduction. Most insect herbivores strongly regulate their nutrient intake when given the opportunity. When they are restricted to imbalanced diets, they employ regulatory rules that govern the extent to which nutrients occurring in excess or deficit are eaten. Insect herbivores also regularly encounter allelochemicals as they eat, and recent work indicates the effect an allelochemical has on nutrient regulation, and insect herbivore performance, is modified depending on a food's nutrient composition. Comparative studies of nutrient regulation suggest coexisting generalist herbivores occupy unique nutritional feeding niches, and work with pathogens and parasitoids has revealed the manner in which top-down pressures influence patterns of nutrient intake. Insect herbivores regulate their nutrient intake using pre- and postingestive mechanisms, plus learning, and there is evidence that some of these mechanisms are shaped by natural selection.

Insect herbivore nutrient regulation.

Nutritional Ecology of Forb Foliage-Chewing Insects Nutritional Ecology of Insect Folivores of Woody Plants: Nitrogen, Water, Fiber and Mineral Considerations Nutritional Ecology of Grass Foliage-Chewing Insects Nutritional Ecology of Phytophagous Mites Nutritional Ecology of Lichen/Moss Arthropods Nutritional Ecology of Arthropod Gall-Makers Nutritional Ecology of Bruchid Beetles Nutritional Ecology of Seed-Sucking Insects Nutritional Ecology of Stored-Product Insects Nutritional Ecology of Stored-Product and House Dust Mites Ecology of Nectar and Pollen Feeding in Lepidoptera.

Frank Slansky

Papers

Nutritional ecology of insects, mites, spiders, and related invertebrates