Microbial Drivers of Sociality – from Multicellularity to Animal Societies

Sociality – the degree to which biological entities form cooperative groups – represents a major transition in the evolution of organismal complexity. Whether at the level of cells or societies, the emergence of collective groups of organisms have dramatically shaped the nature of life on Earth. This is convincingly demonstrated by the fact that multicellular organisms and social insects dominate global ecosystems. For example, multicellular life is thought to be the dominant contributor to global biomass, while ants alone are estimated to make up over a third of the total biomass of insects. Inclusive fitness in combination with environmental conditions can help to explain these transitions, but specific ecological drivers are still under debate. One potential driver that has received only modest attention are microbes, which are universally present in the environment and must be dealt with throughout the life of every organism. In many cases, cooperative groups can be more effective than individual organisms at managing such microbial consortia.

While, for instance, social insect societies possess a broad suite of behavioral and physiological mechanisms to manage both beneficial and pathogenic microbes, the idea that such interactions might act as direct drivers of social traits has hardly been examined. Significantly, there are indications that cell differentiation in concert with conserved molecular pathways may be closely linked to immunity at the origin of animal multicellularity – i.e. defense against antagonistic microbes. This is further corroborated by studies on the facultative multicellular slime-mould, Dictyostelium showing the existence of dedicated sacrificial scavenging cells that engulf foreign and/or pathogenic microbes.

All of these findings support the idea that the emergence of organismal complexity is deeply intertwined with and may even depend upon the evolution of effective molecular, cellular and behavioral strategies to manage mutualistic interactions with beneficial microbes, while simultaneously defending collectively against pathogens. In this Research Topic we seek to extend this concept by exploring how interactions between hosts and microbes can act as general drivers of sociality.

We are particularly interested in assembling research and review articles that draw connections between microbes and social traits across a broad range of ecological and evolutionary scales and even different levels of biological organization, from single cells to animal groups and societies. Contributions from theoretical as well as experimental research are highly encouraged, as are studies examining the mechanistic underpinnings of social traits or evolutionary approaches aimed at understanding ultimate drivers of sociality. Likewise, we are keen to incorporate articles covering a diverse range of taxa (including single-celled organisms, invertebrates and vertebrates) and disciplines, from behavioral ecology, physiology, immunology, microbiology, molecular and cell biology as well as genomics, with studies of an interdisciplinary nature being particularly welcomed.