Killingback Timothy, Blok Hendrik J, Doebeli Michael
Department of Mathematics, College of William and Mary, Williamsburg, VA 23187-8795, USA.
J Theor Biol. 2006 Aug 21;241(4):745-50. doi: 10.1016/j.jtbi.2006.01.010. Epub 2006 Feb 20.
Much of the work on extinction events has focused on external perturbations of ecosystems, such as climatic change, or anthropogenic factors. Extinction, however, can also be driven by endogenous factors, such as the ecological interactions between species in an ecosystem. Here we show that endogenously driven extinction events can have a scale-free distribution in simple spatially structured host-parasitoid systems. Due to the properties of this distribution there may be many such simple ecosystems that, although not strictly permanent, persist for arbitrarily long periods of time. We identify a critical phase transition in the parameter space of the host-parasitoid systems, and explain how this is related to the scale-free nature of the extinction process. Based on these results, we conjecture that scale-free extinction processes and critical phase transitions of the type we have found may be a characteristic feature of many spatially structured, multi-species ecosystems in nature. The necessary ingredient appears to be competition between species where the locally inferior type disperses faster in space. If this condition is satisfied then the eventual outcome depends subtly on the strength of local superiority of one species versus the dispersal rate of the other.
许多关于灭绝事件的研究都集中在生态系统的外部扰动上，比如气候变化或人为因素。然而，灭绝也可能由内生因素驱动，例如生态系统中物种之间的生态相互作用。在这里，我们表明，在简单的空间结构宿主 - 寄生体系统中，内生驱动的灭绝事件可以具有无标度分布。由于这种分布的特性，可能存在许多这样的简单生态系统，尽管它们并非严格意义上的永久性存在，但却能持续任意长的时间。我们在宿主 - 寄生体系统的参数空间中识别出一个临界相变，并解释了这与灭绝过程的无标度性质是如何相关的。基于这些结果，我们推测，我们所发现的这种无标度灭绝过程和临界相变可能是自然界中许多空间结构的多物种生态系统的一个特征。必要的因素似乎是物种之间的竞争，其中在局部处于劣势的物种类型在空间中扩散得更快。如果满足这个条件，那么最终结果将微妙地取决于一个物种的局部优势强度与另一个物种的扩散速率。
