Abstract: Differentiating the relative contribution of host genetic background and surrounding environment on microbiome structure is critical to assess how microbial associations are determined and to what degree they contribute to the physiology of their host organisms. Here, we explored the bacterial and Symbiodiniaceae community composition of genetically identical fire coral colonies that inhabit contrasting reef environments. Our data show that there is significant dissimilarity among the bacterial communities of genetically identical colonies that were found in distinct reef habitats, supporting microbiome flexibility as a mechanism of environmental adaptation. At the same time, we identified several bacterial taxa that were characteristic of a given host genotype across habitats. Functional inference based on sequenced genomes of microbiome profiles revealed that environmentally determined taxa supported a functional restructuring of the microbial metabolic network. In contrast, bacteria determined by host genotype were functionally redundant. Analysis of the Symbiodiniaceae community composition revealed that distinct genotypes were associated with different photosynthetic endosymbionts. Our data showed a clear clustering by host genotypes, with few genotype-specific Symbiodinium sequences, while the clustering by reef habitats is less apparent. Taken together, our study shows that the environment and host genotype determine coral microbial association, and as such, argues for a contribution of the microbiome to environmental adaptation (mostly through coral-associated bacteria), in the form of different taxonomic compositions depending on host genotype.

Biography: Caroline is currently a NSERC Postdoctoral Fellow at the Institute for Integrative Biology and Systems (IBIS, University Laval), in collaboration with the California Academy of Sciences. She studied Marine Sciences in Canada and Coral Reef Ecology at the University of Perpignan in France. Caroline then moved to French Polynesia, where she completed her PhD in Biodiversity, Genetics and Evolution at the CRIOBE lab. Her thesis aimed at evaluating the benefits of asexual versus sexual reproduction in the maintenance of both genetic and phenotypic diversity in population of fire corals across variable environments. After completing her PhD, Caroline pursued her research as a Postdoctoral Fellow at the University of La Réunion and the King Abdullah University of Science and Technology, to continue building and expanding her understanding of phenotypic plasticity, and specifically into the microbiome flexibility. Her research interests as a Postdoctoral Fellow aim to test the general hypothesis that metagenome plasticity contributes to the host’s ability to acclimate and adapt to environmental change. She relies on ecological approaches, combined with classical population genetics, genomics and metatranscriptomic, to provide new insights into coral holobiont structure and function.