Social insect intestines are mating nests for Saccharomyces cerevisiae

Sex can be a difficult task for motionless dispersed organisms such as the yeast Saccharomyces cerevisiae. Albeit yeasts are known to mainly asexually reproduce in nature, they should rely on sex to generate new genetic assemblies. Recent studies on the worldwide S. cerevisiae wild biodiversity significantly broadened the yeast population genetics horizons. Nevertheless, indication on where the yeast sexual reproduction can occur is still lacking. Social insects, by vectoring and maintaining yeast cells in the wild and among different environments, guarantee a possible site for yeasts meeting and mating. S. cerevisiae strains isolated from the intestines of social insects show higher heterozygosis than any other wild and human-related isolate, indicating an occurred genome mixing of different yeast lineages. We provide experimental evidence that Saccharomyces sensu stricto strains co-habiting the intestines of social insects can face sexual reproduction, generating inter- and intra-specific hybrids. This indication, rising from the identification and whole-genome sequencing of S. cerevisiae X S. paradoxus and S. cerevisiae X S. bayanus hybrids isolated from the wild V. crabroguts, is mirrored by results obtained in in vitro conditions (Polistes spp. and Apis mellifera). The intestine of social insects is identified as the niche where Saccharomyces spp. can meet and mate, finally acting as yeasts mating nest and contributing in shaping the fungal evolutionary ecology