Experimentally testing the species-habitat size relationship on soil bacteria: A proof of concept

The species-area relationship is one of the most widely reported ecological theories accounting for biodiversity of plants and animals. However, we lack solid experimental data demonstrating whether this key ecological theorem also applies in the microbial world. Here, we conducted a microcosm study to evaluate the role of habitat area in driving the diversity, abundance, composition and functioning (i.e., four enzyme activities linked to organic matter decomposition) of soil bacterial communities. Thus, we aim to evaluate whether the principle of species-area relationship is potentially applicable to soil microbes. We established a fully factorial experimental design of three island sizes (∼9, 50 and 150 cm²) by two sterile soils (low, high resources). After six months of glasshouse incubation, habitat-area was positively related to bacterial richness, relative abundance of Chloroflexi, Verrucomicrobia and δ-proteobacteria, and soil functions in both soils. Soil with higher resources always had the greatest bacterial richness and functions. Our findings provide a proof of concept by demonstrating the potential importance of both habitat-area and resource availability in driving soil bacterial biodiversity and functioning.