Gut microbiota linked with reduced fear of humans in Red Junglefowl has implications for early domestication

Domestication of animals can lead to profound phenotypic modifications within short evolutionary time periods, and for many species behavioural selection is likely at the forefront of this process. Animal studies have strongly implicated that the gut microbiome plays a major role in host behaviour and cognition through the microbiome-gut-brain axis. Consequently, we hypothesise that host gut microbiota may be one of the earliest phenotypes to change as wild animals are domesticated. Here, we examine the gut microbiome community in two selected lines of red junglefowl (the ancestors of domestic chickens), that were selected for either high or low fear of humans up to eight generations. Microbiota profiles revealed taxonomic differences in gut bacteria known to produce neuroactive compounds between the two selection lines. Gut-brain module analysis by means of genome-resolved metagenomics identified enrichment in the microbial synthesis and degradation potential of metabolites associated with fear extinction and reduced anxiety-like behaviours in low fear fowls. In contrast, high fear fowls were enriched in gut-brain modules from the butyrate and glutamate pathways, metabolites associated with fear conditioning. Overall, our results identified differences in the composition and functional potential of the gut microbiota across selection lines that might provide insights into the mechanistic explanations of the domestication process.