Phillips Benjamin L, Brown Gregory P, Travis Justin M J, Shine Richard
School of Biological Sciences, University of Sydney, Sydney, New South Wales 2006, Australia.
Am Nat. 2008 Jul;172 Suppl 1:S34-48. doi: 10.1086/588255.
Current approaches to modeling range advance assume that the distribution describing dispersal distances in the population (the "dispersal kernel") is a static entity. We argue here that dispersal kernels are in fact highly dynamic during periods of range advance because density effects and spatial assortment by dispersal ability ("spatial selection") drive the evolution of increased dispersal on the expanding front. Using a spatially explicit individual-based model, we demonstrate this effect under a wide variety of population growth rates and dispersal costs. We then test the possibility of an evolved shift in dispersal kernels by measuring dispersal rates in individual cane toads (Bufo marinus) from invasive populations in Australia (historically, toads advanced their range at 10 km/year, but now they achieve >55 km/year in the northern part of their range). Under a common-garden design, we found a steady increase in dispersal tendency with distance from the invasion origin. Dispersal kernels on the invading front were less kurtotic and less skewed than those from origin populations. Thus, toads have increased their rate of range expansion partly through increased dispersal on the expanding front. For accurate long-range forecasts of range advance, we need to take into account the potential for dispersal kernels to be evolutionarily dynamic.
当前用于模拟范围扩展的方法假定描述种群中扩散距离的分布（“扩散核”）是一个静态实体。我们在此认为，在范围扩展期间，扩散核实际上是高度动态的，因为密度效应和按扩散能力的空间分类（“空间选择”）推动了扩张前沿扩散增加的进化。使用基于个体的空间明确模型，我们在各种种群增长率和扩散成本下证明了这种效应。然后，我们通过测量来自澳大利亚入侵种群的个体甘蔗蟾蜍（海蟾蜍）的扩散率，来测试扩散核进化转变的可能性（从历史上看，蟾蜍以每年10公里的速度推进其范围，但现在它们在其范围的北部达到了每年>55公里）。在共同花园设计下，我们发现扩散倾向随着与入侵起源地距离的增加而稳步上升。入侵前沿的扩散核比起源种群的扩散核峰度更低且偏度更小。因此，蟾蜍部分地通过在扩张前沿增加扩散来提高其范围扩展速度。为了对范围扩展进行准确的长期预测，我们需要考虑扩散核在进化上具有动态变化的可能性。
