Conserve the germs: the gut microbiota and adaptive potential

Although the diversity of microbial communities (microbiota) inhabiting body niches are of proven importance to health in both humans and non-human animals, the functional importance of these collective genomes (microbiome) to the adaptive potential of their hosts has only recently been considered within a conservation framework. If loss of gut biodiversity threatens the health (and therefore the fitness of individuals), and this loss can be correlated with the adaptive potential of a species in changing environments, measuring functional composition of the microbiota from non-invasive samples, such as faeces and skin swabs, could provide a useful and practical tool for determining conservation priorities. This article reviews the evidence for adaptive potential of microbiota in wild species, and proposes future directions. While there is ample indication of inter- and intra-specific variation in microbiota diversity, there is little evidence that diversity per se confers fitness. However, there are convincing examples showing that microbiota flexibility, composition and function may well be sources of adaptive potential, although case studies are relatively few, and the analytical approaches needed to demonstrate the mechanisms underlying host–microbiota interactions have only recently been developed.