Phylogenetic comparative methods show rare microbial orders with phylogenetic signal in Galapagos endemic land snails (genus: Naesiotus)

Host-associated microbiomes are often known to cluster based on host relatedness in a phenomenon researchers call phylosymbiosis. This pattern suggests that some microbes are evolving with their host, or at least adapting to diverging host lineages in some way. It is important to understand the historical contingencies between hosts and their microbiomes, as they may have impacts on host fitness. In this study, we apply phylogenetic comparative methods to the novel microbial system of Galapagos endemic land snails (Genus: Naesiotus) in order to discover relationships between microbiome composition as well as abundances of individual microbial taxa across the host phylogeny. We find that across species, Naesiotus fecal microbiomes are comprised of relatively abundant and proportionally stable core taxa that do not vary based on the topology of the host tree. Additionally, we find that among the rarer taxa, some report phylogenetic signal, the covariance patterns of which might be linked to the colonization a recent volcano.