Résumé
The physiology, genetic and evolution of Saccharomyces cerevisiae have been well exploited to understand how evolutionary processes shape diversity and how cell functions. However the genetic and evolution of non-model yeast species are much less known. Moreover, the ecology of yeasts remains poorly documented. Yeasts are found in natural habitats as well as in many different domesticated environments. We catalogued the occurrence of yeast species in fermented food products. We found that some yeast species occurred in all products while others are specific to their environment of origin. Focusing on wine and bread ecosystems, we analysed how and where yeasts may be dispersed. Drosopholids carry 15 different yeast species also found in wine and grape suggesting they could be an important reservoir and vector of yeasts. By analysing yeast species composition of grape must and wheat sourdoughs, we found no evidence of terroir and varieties effects suggesting that geography and plant genotypes are not strongly shaping yeast species diversity in our French sampling area. By contrast, for bread, we found that the practice of bakers and the house microbiota have an effect on sourdough’s yeast species composition. The analysis of the fermentation of different species revealed phenotypic convergence of sourdoughs strains but not of strains coming from other environments. Our results highlight the role of human and socio-cultural practices in maintaining yeast species and genetic diversity.