PRIN 2022 - COD. 20225SXSHY - "ECOSaW: Dissecting Eco-Evolutionary feedbacks between Saccharomyces spp and social Wasps" - Finanziamento dell’Unione Europea – NextGenerationEU – missione 4, componente 2, investimento 1.1.

Hybridization is a crucial process for evolution as it potentially results in individuals bearing new genomic settings and modified -potentially improved- fitness (Dagilis et al. 2019). We have recently shown that the budding yeast Saccharomyces cerevisiae is hosted and can mate within the gut of social wasps in natural settings (Stefanini et al. 2016, Stefanini et al. 2014). Contrarily, this environment seems to be a dead-end for the wild cousin of S. cerevisiae, S.paradoxus, which is capable of surviving within only in the gut of social wasps only as a hybrid with S. cerevisiae (Stefanini et al. 2016). Hence, if on one side the wasp gut could help yeasts bypass the post-zygotic reproductive barriers leading to speciation, on the other side yeast strains may be subjected to selection in this environment. Selection may not only occur within the insect intestine (e.g. strains incapable of surviving to this environment) but also at the moment of uptake; in fact, other insects (Drosophila spp.) have shown preferences for some S. cerevisiae strains according to the volatile compounds produced by the different strains through fermentation (Christiaens et al. 2014). In addition to different attractive potentials, different yeasts have also shown additional impacts on the wasp host, e.g. training immunity – prompting the immune system of the host for future encounters of potentially pathogenic microbes (Meriggi et al. 2019). Hence, the Saccharomyces-insect association shows several features making it potentially relevant for the eco- evolutionary paths of both the microorganism and the host. The ECOSaW project is aimed at dissecting eco-evolutionary feedback involved in this association. In particular, through an approach based on the combination of innovative and classical techniques spanning from meta-trascriptomic analysis through sequencing and Genome-Wide Associations analyses, to wasp behavioral tests and host and yeast survival quantification, we will address and pinpoint multiple aspects: i) if different strains are differently attractive to wasps, are these differences mirrored in the yeast fitness within the wasp gut? And, from the wasps' viewpoint, are the most attractive yeasts more beneficial to the host? And, finally, since the wasp intestine is so far the natural environment where yeast mating occurs, does this reflect on a higher fitness of the resulting hybrids in this environment (e.g. are more attractive or survive better)? This project will not only provide us with a detailed description of the yeast-insect association but will also highlight genetic fingerprints of the eco-evolutionary feedbacks between Saccharomyces spp. yeasts and their host social wasps, hence resulting in an unprecedented dissection of the natural cycle and evolution of the two partners in this association.