Brassil Chad E, Abrams Peter A
Department of Zoology, University of Toronto, 25 Harbord St., Toronto, Ont., Canada M5S 3G5.
Theor Popul Biol. 2004 Aug;66(1):71-82. doi: 10.1016/j.tpb.2004.04.001.
Empirical studies of indirect effects mediated by shared enemies have been characterized by several puzzling features: (a) there exist far fewer documented cases than for interactions via shared resources; (b) the majority of empirical studies have measured indirect effects where one of the two reciprocal effects could not be distinguished from zero; (c) there is a lack of documented positive effects mediated by a shared enemy, in spite of several mechanisms that could produce such effects. One potential explanation is that these are statistical expectations over the range of potential species characteristics. We systematically examine the indirect interactions between two hosts with a shared parasitoid across all potential parameter values, using a family of simple models. By including a detection limit for nonzero interspecific effects, we demonstrate that (-,0) indirect interactions between hosts are the most common type for many variants of the model. However, the absence of positive indirect effects in empirical studies constitutes a puzzling inconsistency between the empirical and theoretical literatures.
（a）与通过共享资源介导的相互作用相比，有记录的案例要少得多；（b）大多数实证研究测量的间接效应中，两个相互作用效应之一无法与零区分开来；（c）尽管有几种机制可以产生由共同天敌介导的积极效应，但缺乏相关记录。一种可能的解释是，这些是对潜在物种特征范围内的统计预期。我们使用一系列简单模型，系统地研究了在所有潜在参数值下，具有共同寄生蜂的两个宿主之间的间接相互作用。通过纳入非零种间效应的检测限，我们证明，对于模型的许多变体，宿主之间的（-，0）间接相互作用是最常见的类型。然而，实证研究中缺乏积极的间接效应，这在实证文献和理论文献之间构成了一个令人困惑的不一致之处。
