The Holobiont Evolutionary Interactions Group specialises in the evolutionary history and interactions between a host and its associated community of microorganisms, including the viriome, bacteriome, mycobiome and metazoan parasites. Our main host models include birds and small mammals, with a special focus on the European house mouse hybrid zone. The group has three main lines of research: 1) the use of models of rodent hybrid zones to investigate the limit of pathogen/parasite specificity, the role of recombination in pathogen host jumps and the role of the microbiome in host speciation; 2) the worldwide distribution and ecological diversification of murid rodents, which allows us to search for the microbiomes functioning in host adaptations, including adaptation to a synanthropic life-style; and 3) studying the microbiome and metabolome of feathers and sebaceous glands, with a focus on the contribution of the integumentary microbiome in production of antimicrobial and chemosignalling compounds involved in olfactory communication and antimicrobial protection in birds.