Doebeli Michael, Ruxton Graeme D
Zoology Institute, University of Basel, Rheinsprung 9, CH-4051, Basel, Switzerland.
Division of Environmental and Evolutionary Biology, Graham Kerr Building, University of Glasgow, Glasgow, G12 8QQ, UK.
Evolution. 1997 Dec;51(6):1730-1741. doi: 10.1111/j.1558-5646.1997.tb05097.x.
We study the evolution of dispersal rates in a two patch metapopulation model. The local dynamics in each patch are given by difference equations, which, together with the rate of dispersal between the patches, determine the ecological dynamics of the metapopulation. We assume that phenotypes are given by their dispersal rate. The evolutionary dynamics in phenotype space are determined by invasion exponents, which describe whether a mutant can invade a given resident population. If the resident metapopulation is at a stable equilibrium, then selection on dispersal rates is neutral if the population sizes in the two patches are the same, while selection drives dispersal rates to zero if the local abundances are different. With non-equilibrium metapopulation dynamics, non-zero dispersal rates can be maintained by selection. In this case, and if the patches are ecologically identical, dispersal rates always evolve to values which induce synchronized metapopulation dynamics. If the patches are ecologically different, evolutionary branching into two coexisting dispersal phenotypes can be observed. Such branching can happen repeatedly, leading to polymorphisms with more than two phenotypes. If there is a cost to dispersal, evolutionary cycling in phenotype space can occur due to the dependence of selection pressures on the ecological attractor of the resident population, or because phenotypic branching alternates with the extinction of one of the branches. Our results extend those of Holt and McPeek (1996), and suggest that phenotypic branching is an important evolutionary process. This process may be relevant for sympatric speciation.
我们研究了一个双斑块集合种群模型中扩散率的演化。每个斑块中的局部动态由差分方程给出，这些方程与斑块之间的扩散率共同决定了集合种群的生态动态。我们假设表型由其扩散率给出。表型空间中的进化动态由入侵指数决定，入侵指数描述了一个突变体是否能够侵入给定的常驻种群。如果常驻集合种群处于稳定平衡状态，那么当两个斑块中的种群大小相同时，对扩散率的选择是中性的，而当局部丰度不同时，选择会将扩散率驱动至零。对于非平衡集合种群动态，非零扩散率可以通过选择得以维持。在这种情况下，并且如果斑块在生态上是相同的，扩散率总是会演化至能够诱导同步集合种群动态的值。如果斑块在生态上不同，就可以观察到进化分支为两种共存的扩散表型。这种分支可能会反复发生，导致出现具有两种以上表型的多态性。如果存在扩散成本，由于选择压力对常驻种群生态吸引子的依赖性，或者由于表型分支与其中一个分支的灭绝交替出现，表型空间中可能会发生进化循环。我们的结果扩展了霍尔特和麦克皮克（1996年）的研究结果，并表明表型分支是一个重要的进化过程。这个过程可能与同域物种形成有关。
