Microbially Mediated Chemical Ecology of Animals: A Review of Its Role in Conspecific Communication, Parasitism and Predation

SIMPLE SUMMARY: Symbiotic bacteria and fungi facilitate the acquisition of nutrients to their animal hosts, protect them against predators, parasites and diseases, and, in some ways, modulate complex animal behavior, including communication, by means of chemical signaling. However, odors of symbiotic bacterial origin would not only inform conspecifics of their animal host, but parasites and/or predators may also use those odors to detect their victims. We here review the role of bacterial symbionts on animal communication, and on interactions of their animal hosts with parasites and predators. Moreover, because microbial symbionts can have negative effects on their hosts facilitating predation and parasitism, these enemies could modulate the microbial community of animals, and we reviewed the available evidence supporting this idea. The inclusion of microorganisms in scenarios of communication, parasitism, and predation opens up new avenues of research that will contribute to understanding such interactions. We here elaborate some predictions and provide some guidance for future research. ABSTRACT: Microbial symbionts are nowadays considered of pivotal importance for animal life. Among the many processes where microorganisms are involved, an emerging research avenue focuses on their major role in driving the evolution of chemical communication in their hosts. Volatiles of bacterial origin may underlie chemical communication and the transfer of social information through signals, as well as inadvertent social information. We reviewed the role of microorganisms in animal communication between conspecifics, and, because the microbiome may cause beneficial as well as deleterious effects on their animal hosts, we also reviewed its role in determining the outcome of the interactions with parasites and predators. Finally, we paid special attention to the hypothetical role of predation and parasitism in driving the evolution of the animal microbiome. We highlighted the novelty of the theoretical framework derived from considering the microbiota of animals in scenarios of communication, parasitism, and predation. We aimed to encourage research in these areas, suggesting key predictions that need to be tested to better understand what is one of the main roles of bacteria in animal biology.