Robinet Christelle, Liebhold Andrew M
INRA, UR 633 Zoologie Forestière, F-45075 Orleans, France.
Ecol Appl. 2009 Oct;19(7):1935-43. doi: 10.1890/08-1971.1.
Given the increasing number of biological invasions, there is a crucial need to identify life history traits that promote invasion. Invasiveness reflects capabilities for both establishment after introduction and spread following establishment. In this paper, we explore, via simulation, the interacting effects of dispersal and Allee effects on both invasion processes. Dispersal capability is a trait that has been widely recognized to facilitate invasions. However, dispersal dilutes local population densities in isolated populations and this could strengthen Allee effects, ultimately promoting extinction of invading populations. A spatially explicit, stochastic individual-based model was used to simulate dispersal, mating, and growth in isolated, newly arrived invading populations. We used the invasion of North America by the gypsy moth, Lymantria dispar, as a case study because: (1) a great amount of biological data on the species is available; (2) Allee effects caused by mate location failure are known to play an important role in its establishment and spread; and (3) a dispersal polymorphism has previously been identified (i.e., in some populations adult females are fully capable of flight, but in other populations females are not able to fly). We considered the introduction of a hypothetical number of eggs at a single location, originating from populations with varying female dispersal capabilities, and we then used simulation models to evaluate the population growth rate over two generations as well as spread distance. Nondispersing populations had the highest growth rates and inclusion of even limited dispersal capabilities caused population growth rates to be greatly diminished. The Allee threshold was 700 eggs for nondispersing populations and 1400 eggs for the long-distance dispersing populations. Thus, for an intermediate number of eggs initially introduced, nondispersing populations would most likely establish, whereas dispersing populations would likely become extinct. Spread distance increased linearly with the number of eggs initially introduced in both dispersing and nondispersing populations but rapidly reached a limit for nondispersing populations. Though species capable of long-distance dispersal may invade a larger area than nondispersing species, their growth rates are likely to be considerably lower, and eradication should be easier. Following these results, strategies for managing invasions should be adjusted for the interactions between Allee effects and dispersal.
鉴于生物入侵的数量不断增加，迫切需要确定促进入侵的生活史特征。入侵性反映了引入后定殖以及定殖后扩散的能力。在本文中，我们通过模拟探讨扩散和阿利效应（Allee effect）对这两个入侵过程的相互作用。扩散能力是一个已被广泛认可的有助于入侵的特征。然而，扩散会稀释孤立种群中的当地种群密度，这可能会强化阿利效应，最终促使入侵种群灭绝。我们使用了一个空间明确的、基于个体的随机模型来模拟孤立的、新到达的入侵种群中的扩散、交配和生长。我们以舞毒蛾（Lymantria dispar）入侵北美为例进行研究，原因如下：（1）该物种有大量的生物学数据；（2）已知由寻找配偶失败导致的阿利效应在其定殖和扩散中起重要作用；（3）此前已鉴定出一种扩散多态性（即，在一些种群中成年雌性完全能够飞行，但在其他种群中雌性无法飞行）。我们考虑在单个地点引入假设数量的卵，这些卵来自具有不同雌性扩散能力的种群，然后我们使用模拟模型评估两代内的种群增长率以及扩散距离。不扩散的种群具有最高的增长率，即使引入有限的扩散能力也会导致种群增长率大幅下降。不扩散种群的阿利阈值为700个卵，远距离扩散种群的阿利阈值为1400个卵。因此，对于最初引入的中等数量的卵，不扩散种群最有可能定殖，而扩散种群可能会灭绝。扩散距离在扩散和不扩散种群中均与最初引入的卵的数量呈线性增加，但不扩散种群很快达到极限。虽然能够远距离扩散的物种可能比不扩散的物种入侵更大的区域，但其增长率可能会低得多，并且根除应该更容易。根据这些结果，应针对阿利效应和扩散之间的相互作用调整入侵管理策略。
