Noonburg Erik G, Abrams Peter A
Department of Zoology, University of Toronto, Toronto, Ontario M5S 3G5, Canada.
Am Nat. 2005 Mar;165(3):322-35. doi: 10.1086/428068. Epub 2005 Jan 20.
We analyze the transient dynamics of simple models of keystone predation, in which a predator preferentially consumes the dominant of two (or more) competing prey species. We show that coexistence is unlikely in many systems characterized both by successful invasion of either prey species into the food web that lacks it and by a stable equilibrium with high densities of all species. Invasion of the predator-resistant consumer species often causes the resident, more vulnerable prey to crash to such low densities that extinction would occur for many realistic population sizes. Subsequent transient cycles may entail very low densities of the predator or of the initially successful invader, which may also preclude coexistence of finite populations. Factors causing particularly low minimum densities during the transient cycles include biotic limiting resources for the prey, limited resource partitioning between the prey, a highly efficient predator with relatively slow dynamics, and a vulnerable prey whose population dynamics are rapid relative to the less vulnerable prey. Under these conditions, coexistence of competing prey via keystone predation often requires that the prey's competitive or antipredator characteristics fall within very narrow ranges. Similar transient crashes are likely to occur in other food webs and food web models.
我们分析了关键捕食简单模型的瞬态动力学，在该模型中，捕食者优先捕食两种（或更多种）竞争猎物物种中的优势物种。我们表明，在许多系统中，共存不太可能发生，这些系统的特征是：要么两种猎物物种中的任何一种成功侵入缺乏该物种的食物网，要么所有物种都处于高密度的稳定平衡状态。抗捕食者的消费者物种的侵入通常会导致本地更易受攻击的猎物数量锐减至如此低的密度，以至于对于许多现实的种群规模而言，灭绝将会发生。随后的瞬态循环可能导致捕食者或最初成功侵入的物种密度极低，这也可能排除有限种群的共存。在瞬态循环期间导致特别低的最小密度的因素包括：猎物的生物限制资源、猎物之间有限的资源分配、具有相对缓慢动态的高效捕食者，以及相对于较不易受攻击的猎物而言种群动态快速的易受攻击的猎物。在这些条件下，通过关键捕食实现竞争猎物的共存通常要求猎物的竞争或反捕食特征落在非常狭窄的范围内。类似的瞬态崩溃很可能在其他食物网和食物网模型中发生。
