Spatial-scale independence of soil bacterial communities in Malaysian tropical forests

Spatial scaling to some extent determines biodiversity patterns in larger organisms, but its role on microbial diversity patterns is much less understood. Some studies have shown that bacterial community similarity decreases with distance, whereas others do not support this. Here we studied soil bacterial communities of tropical rainforest in Malaysia at two spatial scales: a local scale, with samples spaced every 5 meter over 150 meters, and a regional scale with samples 1 to 1800 kilo meter apart. Bacterial communities from soil were determined by pyrosequencing for the 16S rRNA gene. Our results show a minor correlation of spatial distance and community similarity, and only at the local scale. In contrast, environmental dissimilarity was highly correlated with community similarity at both spatial scales; nitrogen content and pH were the only significant environmental variables in explaining community similarity. Dispersal limitation and large scale environmental heterogeneity appear to be of little importance in governing the soil bacterial flora in the Malaysian rainforest. Our results may be taken as evidence against a neutral mechanism of coexistence dependent on broad scale dispersal lags. However, it remains possible that dispersal lag or environmental heterogeneity is important in community scaling at a scale finer than was sampled here.