Phylosymbiosis, diet and gut microbiome-associated metabolic disease

Microbiomes are influenced both by host evolutionary history and ecological context. Phylosymbiosis has been proposed as a framework to understand how evolutionary relationships among hosts predict the structure of the gut microbiome [1]. In this scenario, a hierarchical tree of similarities among host-associated microbiomes would mirror a phylogenetic tree of evolutionary relationships among hosts (Fig. 1). Phylosymbiosis can arise through coevolution and also through environmental, dietary or physiological similarities that correspond with shared evolutionary history. Patterns of phylosymbiosis in the gut microbiome have been observed in multiple groups of animals [2]. However, this is but one eco-evolutionary process that shapes the composition of hostassociated microbiomes. At times, host ecology plays a larger role in structuring microbial communities [3, 4]. There is mounting evidence that humanassociated gut microbiomes do not necessarily follow a pattern of phylosymbiosis [4, 5]. Within the human microbiome, there are bacteria that have coevolved with their host, and others that have not [5]. EXAMPLES IN CLINICAL MEDICINE AND PUBLIC HEALTH