The effects of early-life ambient temperature on the gut microbiome of a wild bird? an experimental approach

Vertebrate gut microbiome has significant effects on host development, health, and fitness. Multiple external factors contribute to gut microbiome variation, and the role of ambient temperature has gained increasing attention. Yet, temperature effects are often tested in extremes and in captive systems. We experimentally studied the effect of subtle temperature decreases during post-natal development on gut microbiome diversity and composition in wild pied flycatchers (Ficedula hypoleuca). We also performed partial cross-fostering to study the relative contribution of genetic and rearing environment on microbiome. Nest-box cold treatment did not influence gut microbiome diversity or composition, which may be due to the small temperature change, ontogenetic stage, or other factors, such as diet, causing large variation in the data. Rearing environment explained more of the variation in gut microbiome than genetic background, but the variance explained was relatively small. Future studies need to further address the drivers of the large intraspecific variation in microbiome in natural populations.