Captivity systematically alters the composition yet not the diversity of vertebrate gut microbiomes

There is an open debate on whether and how captivity alters the gut microbiota of vertebrates, due to the contrasting results reported in different taxa and the absence of systematic multi-species analyses. We performed a meta-analysis of gut microbiota profiles of 322 captive and 322 wild specimens from 24 vertebrate species, including fish, reptiles, amphibians and mammals. We found no evidence that captivity either systematically depletes or increases their gut microbiota. In 88% of the species analysed, although captivity entailed a loss of a fraction of the diversity found in the wild, this was compensated through recruitment of a proportionally similar amount of new taxa only found in captivity. We show such compositional changes can impact evolutionary and ecological inferences that rely on hierarchical clustering-based comparative analyses of gut microbial communities across species.