Data from: Tradeoffs, spatial heterogeneity, and the maintenance of microbial diversity

Specialization and concomitant tradeoffs are assumed to underlie the non-neutral coexistence of lineages. Tradeoffs across heterogeneous environments can promote diversity by preventing competitive exclusion. However, the importance of tradeoffs in maintaining diversity in natural microbial assemblages is unclear, as tradeoffs are frequently not detected in artificial evolution experiments. Stressful conditions associated with patches of heavy-metal enriched serpentine soils provide excellent opportunities for examining how heterogeneity may foster genetic diversity. Using a spatially-replicated design, we demonstrate that rhizobium bacteria symbiotic with legumes inhabiting contrasting serpentine and non-serpentine soils exhibit a tradeoff between a genotype’s nickel tolerance and its ability to replicate rapidly. Furthermore, we detected adaptive divergence in rhizobial assemblages across soil type heterogeneity at multiple sites, suggesting that this tradeoff may promote the coexistence of phenotypically distinct bacterial lineages. Tradeoffs and adaptive divergence may be important factors maintaining the tremendous diversity within natural assemblages of bacteria.特化及其伴随的权衡效应，被认为是细菌谱系非中性共存的核心机制。异质环境中的权衡效应可通过阻断竞争性排除，进而促进谱系多样性的维持。然而，权衡效应在自然微生物群落多样性维持中的实际重要性仍不明确，这是因为人工进化实验中往往难以检测到这类权衡现象。富含重金属的蛇纹岩土斑块所构成的胁迫环境，为探究环境异质性如何推动遗传多样性形成提供了绝佳研究模型。本研究采用空间重复实验设计，证实栖息于蛇纹岩土与非蛇纹岩土这两种截然不同生境中的豆科植物共生根瘤菌（rhizobium），其基因型的镍耐受能力与快速繁殖能力之间存在显著权衡效应。此外，我们在多个样点的土壤类型异质性环境中，检测到根瘤菌群落存在适应性分化，这表明该权衡效应或可推动表型各异的细菌谱系实现共存。权衡效应与适应性分化，或为维持自然细菌群落极高谱系多样性的关键驱动因素。