Social interactions across groups of colobus monkeys (Colobus vellerosus) explain similarities in their gut microbiomes
The gut microbiome is structured by social groups in a variety of host taxa. Whether this pattern is driven by relatedness, similar diets, or shared social environments is under debate because few studies have had access to the data necessary to disentangle these factors in wild populations. We investigated whether diet, relatedness, or the 1-meter proximity network best explains differences in the gut microbiome among 45 female colobus monkeys in 8 social groups residing at Boabeng-Fiema, Ghana. We combined demographic and behavioural data collected May-August 2007 and October 2008-April 2009 with 16S rRNA sequencing of faecal samples collected during the latter part of each observation period. Social group identity explained a large percentage of the variation in gut microbiome beta-diversity. When comparing the predictive power of dietary dissimilarity, relatedness, and connectedness in the 1-meter proximity network, the models with social connectedness received the strongest support, even in our analyses that excluded within-group dyads. This novel finding indicates that microbes may be transmitted during intergroup encounters, which could occur either indirectly via shared environments or directly via social contact. Lastly, some of the gut microbial taxa that appear to be transmitted via 1-meter proximity are associated with digestion of plant material, but further research is needed to investigate whether this type of gut microbe transmission yields health benefits, which could provide an incentive for the formation and maintenance of social bonds within and between social groups.