American Society of Naturalists

A membership society whose goal is to advance and to diffuse knowledge of organic evolution and other broad biological principles so as to enhance the conceptual unification of the biological sciences.

“Soil microbes generate stronger fitness differences than stabilization among California annual plants”

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Gaurav S. Kandlikar (गौरव कांडलिकर), Xinyi Yan (严心怡), Jonathan M. Levine, and Nathan J. B. Kraft (Jan 2021)

Soil microbes can both promote and hinder plant diversity in California grasslands

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Soil microorganisms influence a variety of processes in plant communities. Many theoretical and empirical studies have shown that dynamic feedbacks between plants and soil microbes can stabilize plant coexistence by generating negative frequency-dependent plant population dynamics. However, inferring the net effects of soil microbes on plant coexistence requires also quantifying the degree to which they provide one species an average fitness advantage, an effect that has received little empirical attention. We conducted a greenhouse study to quantify microbially mediated stabilization and fitness differences among fifteen pairs of annual plants that co-occur in southern California grasslands. We found that although soil microbes frequently generate negative frequency-dependent dynamics that stabilize plant interactions, they simultaneously generate large average fitness differences between species. The net result is that if the plant species are otherwise competitively equivalent, the impact of plant-soil feedbacks is to often favor species exclusion over coexistence, a result that only becomes evident by quantifying the microbially mediated fitness difference. Our work highlights that comparing the stabilizing effects of plant-soil feedbacks to the fitness difference they generate is essential for understanding the influence of soil microbes on plant diversity.


土壤微生物影响植物种群的多种生态过程。许多理论和实验研究已表明,植物和土壤微生物之间的动态反馈,可以引起植物种群的负频率制约,从而稳定物种的共存关系。然而,推断土壤微生物对于植物种共存的实际影响,还需要量化它们给予共存种平均适合度的相对优势。然而,以前很少有研究关注这个效应。 我们通过一个温室实验,测量微生物在15对共生于南加州草原一年生植物之间产生的稳定化机制和适合度差异。结果表明,尽管土壤微生物经常引起有助于稳定植物共生关系的负频率制约,它们同时也导致植物物种之间出现较大的适合度差异。综合两者,假设这些共存的植物种在其他方面的竞争优势相同,植物-土壤反馈往往促进物种间的竞争排斥,而不是共存。这一结论只有通过量化微生物介导的适合度差异才能做出。本研究强调,比较植物-土壤微生物反馈引起的稳定化机制和适合度差异,对于理解土壤微生物对植物多样性的影响具有重要的意义。