Department of Biology, Stanford University, 371 Serra Mall, Stanford, CA 94305, USA.
Proc Biol Sci. 2012 Feb 22;279(1729):749-58. doi: 10.1098/rspb.2011.1230. Epub 2011 Jul 20.
Priority effects, in which the outcome of species interactions depends on the order of their arrival, are a key component of many models of community assembly. Yet, much remains unknown about how priority effects vary in strength among species in a community and what factors explain this variation. We experimented with a model natural community in laboratory microcosms that allowed us to quantify the strength of priority effects for most of the yeast species found in the floral nectar of a hummingbird-pollinated shrub at a biological preserve in northern California. We found that priority effects were widespread, with late-arriving species experiencing strong negative effects from early-arriving species. However, the magnitude of priority effects varied across species pairs. This variation was phylogenetically non-random, with priority effects stronger between closer relatives. Analysis of carbon and amino acid consumption profiles indicated that competition between closer relatives was more intense owing to higher ecological similarity, consistent with Darwin's naturalization hypothesis. These results suggest that phylogenetic relatedness between potential colonists may explain the strength of priority effects and, as a consequence, the degree to which community assembly is historically contingent.
优先效应是指物种相互作用的结果取决于它们到达的顺序，是许多群落组装模型的关键组成部分。然而，关于优先效应在群落中物种间的强度如何变化以及哪些因素解释了这种变化，我们仍然知之甚少。我们在实验室微宇宙中用一个模型自然群落进行了实验，该实验使我们能够量化在加利福尼亚州北部一个生物保护区的蜂鸟授粉灌木的花蜜中发现的大多数酵母物种的优先效应的强度。我们发现优先效应很普遍，晚到的物种会受到早到的物种的强烈负面影响。然而，优先效应的幅度在物种对之间存在差异。这种变异在系统发育上是非随机的，亲缘关系较近的物种之间的优先效应更强。对碳和氨基酸消耗谱的分析表明，由于生态相似性更高，亲缘关系较近的物种之间的竞争更加激烈，这与达尔文的自然化假说一致。这些结果表明，潜在殖民者之间的系统发育关系可能解释了优先效应的强度，以及群落组装在多大程度上具有历史偶然性。
