Undead food-webs: Integrating microbes into the food-chain

Authors: Steffan, Shawn; DHARAMPAL, PRARTHANA - University Of Wisconsin

Submitted to: FOOD WEBS
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/14/2018
Publication Date: 3/1/2019
Citation: Steffan, S.A., Dharampal, P.S. 2019. Undead food-webs: Integrating microbes into the food-chain. Food Webs. 16(e00111). https://doi.org/10.1016/j.fooweb.2018.e00111.
DOI: https://doi.org/10.1016/j.fooweb.2018.e00111

Interpretive Summary: Microbes dominate all major ecosystem types, whether natural or agricultural. This review examines historical and more contemporary models of food-webs, and makes the case that when microbes are considered as intrinsic elements of food-chains, the functional roles of other organisms change, but these changes represent a more accurate portrayal of function. Microbial communities maintain a wide variety of symbioses with arthropods, and this review describes a new framework within which insects (and other animals) can be considered as symbionts of microbes. Agricultural scientists who investigate the functioning of agro-ecosystems will benefit from understanding the roles of microbes within the food-chain will dramatically improve our understanding of how food-webs (whether agricultural or non-managed) function.

Technical Abstract: Detritivory represents the dominant trophic mode on Earth, and within this vast consumer group, microbes tend to predominate. Virtually all detritus is replete with microbes, many of which consume the detrital substrate, rendering it a complex of living and non-living components. A detrital mass, therefore, can be considered an ‘undead’ food-web in which the resident microbes busily displace non-living biomass with their own, while carnivorous microbes prey upon other organisms. In this food-chain, bacteria and fungi have been shown to register just as animals do, demonstrating that microbes are analogous to animals within trophic hierarchies. Given that microbial consumers are often suffused throughout detrital substrates, the detritus becomes a complex of multiple trophic groups. It has long been suggested that microbial consumers within soil systems represent distinct trophic groups, and in recent studies, these hypotheses have been tested empirically. The detrital complex, then, can be considered a dynamic microcosm of the broader food-web, and the trophic identities within the complex (as well as the metazoans that consume the complex), can be measured and interpreted. This multi-trophic aspect of ‘undead’ detritus tends to elevate the trophic positions of animals (i.e., trophic inflation), which derives from the assimilation of heterotrophic (microbial) and autotrophic proteins. Importantly, inclusion of microbes in trophic hierarchies provides a more comprehensive framework within which to interpret organismal-, population-, and community-scale trophic identities. However, in recalibrating our trophic ‘lens’ to include microbial consumers, there remain some long-standing concepts, questions, and definitions that will need to be revisited.