W. K. Kellogg Biological Station, Department of Plant Biology, Michigan State University, East Lansing, Michigan 48824, USA.
Ecology. 2012 Apr;93(4):711-8. doi: 10.1890/11-1358.1.
Theory suggests that cheaters threaten the persistence of mutualisms, but that sanctions to prevent cheating can stabilize mutualisms. In the arbuscular mycorrhizal symbiosis, reports of parasitism suggest that reductions in plant carbon allocation are not universally effective. I asked whether plant species differences in mycorrhizal responsiveness would affect both their susceptibility to parasitism and their reduction in allocation to non-beneficial arbuscular mycorrhizal fungi (AMF) in high-phosphorus soils. In a greenhouse experiment, I found that two C3 grasses, Bromus inermis and Elymus repens, effectively suppressed root colonization and AMF hyphal abundance. Increases in soil phosphorus did not reduce the degree to which AMF increased plant biomass. In contrast, two C4 grasses, Andropogon gerardii and Schizachyrium scoparium, more weakly reduced root colonization and failed to suppress AMF hyphal abundance. Consequently, they experienced strong declines in their response to AMF, and one species suffered parasitism. Thus, species differ in susceptibility to parasitism and their reduction in allocation to non-beneficial AMF. These differences may affect the distribution and abundance of plants and AMF, as well as the stability of the mutualism.
理论认为骗子会威胁到共生关系的持续存在，但防止作弊的制裁可以稳定共生关系。在丛枝菌根共生关系中，寄生的报道表明，植物对碳的分配减少并不总是有效的。我想知道植物对菌根反应的种间差异是否会影响它们对寄生的易感性以及它们在高磷土壤中对非有益丛枝菌根真菌（AMF）分配的减少。在温室实验中，我发现两种 C3 草，无芒雀麦和偃麦草，有效地抑制了根的定殖和 AMF 菌丝的丰度。土壤中磷的增加并没有降低 AMF 增加植物生物量的程度。相比之下，两种 C4 草，狗尾草和柳枝稷，较弱地减少了根的定殖，并且未能抑制 AMF 菌丝的丰度。因此，它们对 AMF 的反应明显减弱，其中一种受到了寄生。因此，物种在对寄生的易感性和对非有益 AMF 的分配减少方面存在差异。这些差异可能会影响植物和 AMF 的分布和丰度，以及共生关系的稳定性。
