The plant species component of mangrove communities is highly similar among geographic locations even across the global scale. However, the rhizosphere bacterial communities are highly geographically structured. To uncover the mechanism shaping bacterial community assembly and connectivity at the regional scale, we compared 136 samples of rhizosphere and bulk sediment from 17 mangrove sites along the coast of southeast China.
We found that the community similarity between sites was majorly correlated with geographic distance, as indicated by PCoA, variance partitioning analysis (VPA), beta diversity decomposition, and the phylogenetic-bin-based null model analysis (iCAMP). Consistently, dispersal limitation was found to be the dominant mechanism shaping bacterial community assembly. The proportion of dispersal limitation is positively correlated with geographic distance, which is mostly contributed by the phylogenetic bins belonging to Proteobacteria. There are also some bacterial taxa that are constraint by both geographic distance and soil carbon content in dispersal ability. We conducted a cellular automata simulation, showing that specialists are enriched in high-carbon areas through higher birth rates and dispersal preferences, while generalists distribute more evenly in the entire spatial space.
These results elucidate the mechanism underlying the high dispersal limitation across geographic distances of the phylogenetic taxa associated with carbon decomposition, which further shapes the differentiation of bacterial communities among different sites at the regional scale.