Division of Biological Sciences, University of Montana, Missoula, Montana 59812, USA.
Ecology. 2011 May;92(5):1027-35. doi: 10.1890/10-0089.1.
The net effects of soil biota on exotic invaders can be variable, in part, because net effects are produced by many interacting mutualists and antagonists. Here we compared mutualistic and antagonistic biota in soils collected in the native, expanded, and invasive range of the black locust tree, Robinia pseudoacacia. Robinia formed nodules in all soils with a broad phylogenetic range of N-fixing bacteria, and leaf N did not differ among the different sources of soil. This suggests that the global expansion of Robinia was not limited by the lack of appropriate mutualistic N-fixers. Arbuscular mycorrhizal fungi (AMF) from the native range stimulated stronger positive feedbacks than AMF from the expanded or invasive ranges, a biogeographic difference not described previously for invasive plants. Pythium taxa collected from soil in the native range were not more pathogenic than those from other ranges; however, feedbacks produced by the total soil biota were more negative from soils from the native range than from the other ranges, overriding the effects of AMF. This suggests that escape from other pathogens in the soil or the net negative effects of the whole soil community may contribute to superior performance in invaded regions. Our results suggest that important regional evolutionary relationships may occur among plants and soil biota, and that net effects of soil biota may affect invasion, but in ways that are not easily explained by studying isolated components of the soil biota.
土壤生物群对入侵种的净效应可能是多样的，部分原因是净效应是由许多相互作用的共生体和拮抗体产生的。在这里，我们比较了原产、扩展和入侵地区的刺槐土壤中的共生体和拮抗体。刺槐在所有土壤中都形成了根瘤，其中包含了广泛的固氮细菌，并且不同来源的土壤中的叶片氮含量没有差异。这表明刺槐的全球扩张并没有受到缺乏合适的共生固氮体的限制。与扩展或入侵地区的丛枝菌根真菌（AMF）相比，原产地区的 AMF 能产生更强的正反馈，这是以前没有描述过的入侵植物的生物地理差异。从原产地区土壤中收集到的腐霉属类群并不比其他地区的腐霉属类群更具致病性；然而，来自原产地区土壤的总土壤生物群产生的反馈比来自其他地区的土壤更负，这抵消了 AMF 的作用。这表明，从土壤中的其他病原体中逃脱，或者整个土壤群落的净负面影响可能有助于在入侵地区的优异表现。我们的研究结果表明，植物和土壤生物群之间可能存在重要的区域进化关系，土壤生物群的净效应可能会影响入侵，但以研究土壤生物群的孤立成分难以解释的方式。
