Zhang Zhijie, Liu Yanjie, Brunel Caroline, van Kleunen Mark
Ecology, Department of Biology, University of Konstanz, Konstanz, Germany.
Key Laboratory of Wetland Ecology and Environment, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Changchun, China.
Nat Ecol Evol. 2020 Dec;4(12):1612-1621. doi: 10.1038/s41559-020-01311-0. Epub 2020 Oct 5.
While most alien species fail to establish, some invade native communities and become widespread. Our understanding of invasion success is derived mainly from pairwise interactions between aliens and natives, while interactions among more than two species remain largely unexplored. Here, we experimentally tested whether and how a third plant species, either native or alien, affected the competitive outcomes between alien and native plants through its soil legacy. We first conditioned soil with one of ten species (six natives and four aliens) or without plants. We then grew on these 11 soils five aliens and five natives without competition, or with intra- or interspecific competition. We found that aliens were not more competitive than natives when grown on soil conditioned by other natives or on non-conditioned soil. However, aliens were more competitive than natives on soil conditioned by other aliens (that is, invasional meltdown). Soil conditioning did not change competitive outcomes by affecting the strength of competition between later plants. Instead, soil conditioned by aliens pushed competitive outcomes towards later aliens by affecting the growth of aliens less negatively than that of natives. Microbiome analysis verified this finding, as we showed that the soil-legacy effects of a species on later species were less negative when their fungal endophyte communities were less similar, and that fungal endophyte communities were less similar between two aliens than between aliens and natives. Our study reveals invasional meltdown in multispecies communities and identifies soil microorganisms as a driver of the invasion success of alien plants.
虽然大多数外来物种无法立足，但有些会入侵本地群落并广泛传播。我们对入侵成功的理解主要源于外来物种与本地物种之间的成对相互作用，而对于两个以上物种之间的相互作用，很大程度上仍未得到探索。在这里，我们通过实验测试了第三种植物物种（本地或外来）是否以及如何通过其土壤遗留物影响外来植物与本地植物之间的竞争结果。我们首先用十种物种（六种本地物种和四种外来物种）中的一种对土壤进行预处理，或者不使用植物进行预处理。然后，我们在这11种土壤上种植了五种外来植物和五种本地植物，它们之间不存在竞争，或者存在种内或种间竞争。我们发现，当在由其他本地物种预处理的土壤或未预处理的土壤上生长时，外来植物并不比本地植物更具竞争力。然而，在由其他外来物种预处理的土壤上，外来植物比本地植物更具竞争力（即入侵崩溃）。土壤预处理并没有通过影响后期植物之间的竞争强度来改变竞争结果。相反，由外来物种预处理的土壤通过对外来植物生长的负面影响小于对本地植物的负面影响，将竞争结果推向了后期的外来植物。微生物群落分析证实了这一发现，因为我们表明，当两个物种的真菌内生菌群落相似度较低时，一个物种对后期物种的土壤遗留效应的负面影响较小，并且两个外来物种之间的真菌内生菌群落相似度低于外来物种与本地物种之间的相似度。我们的研究揭示了多物种群落中的入侵崩溃现象，并确定土壤微生物是外来植物入侵成功的一个驱动因素。
