Bever James D, Richardson Sarah C, Lawrence Brandy M, Holmes Jonathan, Watson Maxine
Department of Biology, Indiana University, Bloomington, IN 47405, USA.
Ecol Lett. 2009 Jan;12(1):13-21. doi: 10.1111/j.1461-0248.2008.01254.x. Epub 2008 Oct 21.
Mutualisms, beneficial interactions between species, are expected to be unstable because delivery of benefit likely involves fitness costs and selection should favour partners that deliver less benefit. Yet, mutualisms are common and persistent, even in the largely promiscuous associations between plants and soil microorganisms such as arbuscular mycorrhizal fungi. In two different systems, we demonstrate preferential allocation of photosynthate by host plants to the more beneficial of two AM fungal symbionts. This preferential allocation could allow the persistence of the mutualism if it confers sufficient advantage to the beneficial symbiont that it overcomes the cost of mutualism. We find that the beneficial fungus does increase in biomass when the fungi are spatially separated within the root system. However, in well-mixed fungal communities, non-beneficial fungi proliferate as expected from their reduced cost of mutualism. Our findings suggest that preferential allocation within spatially structured microbial communities can stabilize mutualisms between plants and root symbionts.
互利共生，即物种间的有益相互作用，预计是不稳定的，因为提供益处可能涉及适合度成本，而选择应有利于提供较少益处的伙伴。然而，互利共生很常见且持久，即使在植物与土壤微生物（如丛枝菌根真菌）之间大体上混杂的关联中也是如此。在两个不同的系统中，我们证明了宿主植物会将光合产物优先分配给两种丛枝菌根真菌共生体中更有益的一方。如果这种优先分配赋予有益共生体足够的优势，使其能够克服互利共生的成本，那么它可能会使互利共生得以持续。我们发现，当真菌在根系内空间分离时，有益真菌的生物量确实会增加。然而，在充分混合的真菌群落中，非有益真菌如预期那样因其较低的互利共生成本而增殖。我们的研究结果表明，在空间结构的微生物群落内进行优先分配可以稳定植物与根系共生体之间的互利共生关系。
