Hoverman Jason T, Relyea Rick A
Department of Biological Sciences, University of Pittsburgh, Pittsburgh, PA 15260, USA.
Oecologia. 2007 Dec;154(3):551-60. doi: 10.1007/s00442-007-0847-3. Epub 2007 Sep 9.
Studies of inducible defenses have traditionally examined prey responses to one predator at a time. However, prey in nature encounter combinations of predators that should force them to produce phenotypic compromises. We examined how snails (Helisoma trivolvis) alter their phenotype in the presence of three different predator species that were presented alone and in pairwise combinations. When snails were exposed to each predator alone, they formed predator-specific defenses that reflected the differences in each predator's foraging mode. When snails were exposed to pairwise combinations of predators, their phenotype was dependent on their ability to detect each predator, the risk posed by each predator, and the effectiveness of a given defense against each predator. Consequently, responses to combined predators were typically biased towards one of the predators in the pair. This suggests that prey facing combined predators do not form simple intermediate defenses and, as a result, may experience enhanced mortality risk when they encounter natural predator regimes.
对诱导性防御的研究传统上每次只考察猎物对一种捕食者的反应。然而，自然界中的猎物会遭遇多种捕食者的组合，这应该会迫使它们做出表型上的妥协。我们研究了蜗牛（三带扁卷螺）在面对单独呈现以及成对组合呈现的三种不同捕食者物种时如何改变其表型。当蜗牛单独暴露于每种捕食者时，它们形成了特定于捕食者的防御机制，这反映了每种捕食者觅食方式的差异。当蜗牛暴露于捕食者的成对组合时，它们的表型取决于它们检测每种捕食者的能力、每种捕食者带来的风险以及特定防御对每种捕食者的有效性。因此，对组合捕食者的反应通常偏向于成对中的一种捕食者。这表明面对组合捕食者的猎物不会形成简单的中间防御机制，因此，当它们遇到自然捕食者组合时，可能会面临更高的死亡风险。
