Department of Botany and Biodiversity Research Center, University of British Columbia, Vancouver, British Columbia V6T1Z4, Canada.
Am Nat. 2009 Dec;174(6):850-62. doi: 10.1086/647903.
Ecological theories make divergent predictions about whether extant species inhibit or promote the establishment of new species and which aspects of community composition determine these interactions; diversity, individual dominant species, and neutral interactions have all been argued to be most important. We experimentally tested these predictions by removing plant biomass (0%, 7%, 100%) from boreal forest understory communities. The 7% removals were restricted to the numerically dominant species, the second most dominant species, or many low-abundance species, thereby separating the effects of species composition from those of biomass. We tested the effects of all removal treatments on seedling establishment. Competitive effects were driven by one dominant species and were inconsistent with resource complementarity, neutral, or competition-colonization models. Facilitative effects were apparent only following removal of all vegetation, of which the most dominant species comprised more than 80%. Our results indicate that numerically dominant species in a community can influence the establishment of new species more than species diversity, but the direction of interaction can shift from facilitative to competitive as community density increases.
生态理论对现存物种是抑制还是促进新物种的建立做出了不同的预测，以及群落组成的哪些方面决定了这些相互作用；多样性、个体优势物种和中性相互作用都被认为是最重要的。我们通过从北方森林林下群落中去除植物生物量（0%、7%、100%）来实验测试这些预测。7%的去除仅限于数量上占优势的物种、第二大优势物种或许多低丰度物种，从而将物种组成的影响与生物量的影响区分开来。我们测试了所有去除处理对幼苗建立的影响。竞争效应是由一个优势物种驱动的，与资源互补、中性或竞争-殖民模型不一致。只有在去除所有植被后才会出现促进作用，其中最占优势的物种占 80%以上。我们的结果表明，群落中的数量优势物种对新物种的建立的影响可能大于物种多样性，但随着群落密度的增加，相互作用的方向可能从促进作用转变为竞争作用。
