Understanding the patterns of diversity and composition of species in communities is the primary question in community ecology. Recently, it has also become the main focus of the fast-growing research field of host-associated microbial communities (microbiome). A significant advancement of ecological theory is the understanding that community diversity is a product of factors acting at both the local community level and the broader regional level, and the relative importance of each can provide insights about the mechanisms driving the observed patterns. We applied this idea to a vertebrate gut microbiome system by asking if local effects (species identity of the host) or regional effects (identity of the pond) are more important in shaping the gut microbiome of tadpoles. We sampled bacterial communities of tadpole guts (19 species), water, and substrate from 24 ponds in Brazil and the USA. From each sample, we amplified and sequenced the V4 region of the bacterial 16s rRNA gene. We performed variance partitioning analysis to test the local (species) and regional (pond) influence on tadpole gut microbiome and estimated the source of colonists of the microbiome using source tracking analysis.
Results/Conclusions
Our preliminary results show that regional effects (pond of origin) were more important than local effects (species identity). The regional effects explained over 40% of the variance in tadpole gut microbiome whereas local effects explained less than 5%, and their joint effects explained less than 10%. In general, bacteria from the water column were the main colonizers of the tadpole gut microbiome, and the substrate contributed only to a small proportion. These results show that the tadpole gut microbiome is mostly shaped by the pool of colonists they are exposed to, with species identity playing only a minor role. Understanding that the regional species pool of bacteria is important in shaping the microbiome can have implications, for example, in comprehending inter- and intra-specific differences in the microbiome. Furthermore, attempts to manipulate the microbiome just by changing some aspects of the host might not work as expected if the regional species pool is not considered. The application of ecological theory to microbiome studies can help explain the observed patterns, generate hypotheses, and make predictions. In turn, microbiome systems can be used to test the current ecological theory using its natural microcosm nature or benefiting from the increasing amount of data available.