Presence of microbiota reverses the relative performance of Daphnia on two experimental diet

The outcomes of host–symbiont interactions may differ according to environmental context, and symbioses may enable host adaptation to diverse environments. We find that the effects of two different experimental diets, algae and yeast, on the water flea Daphnia magna depend on whether the animals possess microbiota, suggesting that the presence of microbiota determines which diet is superior. Our study hints at both diet-dependent and diet-independent effects of microbiota on Daphnia fitness.