The microbial dimension in insect nutritional ecology

Abstract

Summary 1.Many 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. 2. There 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.3. Some 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. 4. Developing 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.

Unpredicted impacts of insect endosymbionts on interactions between soil organisms, plants and aphids

“…Further research will be required to understand the mechanistic detail of the complex indirect interactions between plant-soil microbe mutualisms and aphid-bacterial mutualisms. Aphids are not the only agriculturally significant insects to carry facultative endosymbionts [1,5,33], and it has been argued that the ecology and physiology of symbiont-bearing insects cannot be fully understood outside the context of these symbioses [4]. The incorporation of insect symbionts into the design of soil-plant-insect interaction studies could provide further novel insight into the wider ecological significance of facultative symbioses.…”

Divergence across diet, time and populations rules out parallel evolution in the gut microbiomes of Trinidadian guppies

“…Well documented in the mammals and in several insects, specific symbioses related to particular trophic habits are widely argued to reflect the importance of bacteria in host dietary utilization (see, for example, Ley et al, 2008;Russell et al, 2009). Empirical and metagenomic evidence clearly indicate such an importance (Feldhaar et al, 2007;Douglas, 2009;Muegge et al, 2011). Hence, are shifts in bacteria essential for shifts in diet or trophic level?…”

Four Central Points About Coevolution

“…The great majority of plant species would quickly go extinct in nature without the mycorrhizal fungi attached to their roots that aid in nutrient capture or without the pollinators that aid in their reproduction. Animals generally rely on an assortment of gut symbionts to aid in nutrition, and the complexity of those symbioses is only starting to be unraveled (van Borm et al 2002;Douglas 2009;Noda et al 2009;Round and Mazmanian 2009).…”