Communities within communities: Exploring the interaction between tropical land-snails and their microbiome communities

Communities are shaped by yet poorly understood processes like dispersal, drift and selection. Natural communities encompass more than just one taxonomic group or spatial scale, as do the forces that shape these communities. Microbiomes are an integral part of life, and also part of their host’s community. They are often vital to their host’s functioning and are continuously shaped by their host and its environment. It remains unknown, however, if the transfer of microbes between different host species in a community has significant effects on the microbiomes within said community. Such effects could have major implications for microbiome functioning, as well as microbiome phylogenies in relation to their host’s. The aim of the study was to investigate microbiome structure and phylogeny across isolated host communities. Using a combination of Borneon microsnail community data and metabarcoding of bacterial communities, we showed that microbial communities diverge along with their host species. We showed that host species isolation is a stronger factor shaping microbiome composition than the community composition of related host species per location. Our results suggest that within-host species dispersal, selection and drift are stronger actors in shaping microbiome than dispersal or transmission of bacteria among host species. Our results underline microbiomes’ potential as an additional source of information on their host’s population dynamics and evolutionary history.