Data from: Soil microbial community variation correlates most strongly with plant species identity, followed by soil chemistry, spatial location and plant genus

Soil ecologists have debated the relative importance of dispersal limitation and ecological factors in determining the structure of soil microbial communities. Recent evidence suggests that "everything is not everywhere", and that microbial communities are influenced by both dispersal limitation and ecological factors. However, we still do not understand the relative explanatory power of spatial and ecological factors, including plant species identity and even plant relatedness, for different fractions of the soil microbial community (i.e. bacterial and fungal communities). To ask whether factors such as plant species, soil chemistry, spatial location, and plant relatedness influence rhizosphere community composition, we examined field-collected rhizosphere soil of seven congener pairs that occur at Bodega Bay Marine Reserve, CA, USA. We characterized differences in bacterial and fungal communities using Terminal-Restriction Fragment Length Polymorphism. Plant species identity was the single best statistical predictor of both bacterial and fungal community composition in the root zone. Soil microbial community structure was also correlated with soil chemistry. The third best predictor of bacterial and fungal communities was spatial location, confirming that everything is not everywhere. Variation in microbial community composition was also related to combinations of spatial location, soil chemistry, and plant relatedness, suggesting that these factors do not act independently. Plant relatedness explained less of the variation than plant species, soil chemistry, or spatial location. Despite some congeners occupying different habitats and being spatially distant, rhizosphere fungal communities of plant congeners were more similar than expected by chance. Bacterial communities from the same samples were only weakly similar between plant congeners. Thus, plant relatedness might influence soil fungal, more than soil bacterial, community composition.土壤生态学家长期围绕扩散限制与生态因子在塑造土壤微生物群落结构中的相对重要性展开争论。最新研究证据表明，“微生物并非无处不在”，土壤微生物群落同时受到扩散限制与生态因子的共同调控。然而，针对土壤微生物群落的不同组分（即细菌群落与真菌群落），我们仍未明确空间因子与各类生态因子（包括植物物种属性乃至植物亲缘关系）的相对解释力。为探究植物物种、土壤化学性质、空间位置以及植物亲缘关系等因子是否会影响根际微生物群落组成，本研究对采自美国加利福尼亚州（CA）博德加湾海洋保护区的7对同属植物的根际土壤样品开展了分析。本研究采用末端限制性片段长度多态性（Terminal-Restriction Fragment Length Polymorphism, T-RFLP）技术对细菌与真菌群落的差异进行表征。结果显示，植物物种属性是根际区域细菌与真菌群落组成的最优单一统计预测因子；土壤微生物群落结构同样与土壤化学性质显著相关。空间位置是影响细菌与真菌群落的第三大预测因子，这一结果印证了“微生物并非无处不在”的结论。微生物群落组成的变异同时与空间位置、土壤化学性质以及植物亲缘关系的组合效应相关，表明上述因子并非独立发挥作用。相较于植物物种、土壤化学性质与空间位置，植物亲缘关系对群落变异的解释度更低。尽管部分同属植物栖息于不同生境且空间距离较远，但同属植物的根际真菌群落相似度仍显著高于随机预期水平；而同属植物根际细菌群落的相似性则仅处于较低水平。由此可见，植物亲缘关系对土壤真菌群落组成的影响要强于其对土壤细菌群落的影响。