Biology Department, Washington University, St Louis, MO 63130, USA.
Proc Biol Sci. 2010 Jul 22;277(1691):2185-91. doi: 10.1098/rspb.2009.2344. Epub 2010 Mar 17.
The outcome of competitive interactions is likely to be influenced by both competitive dominance (i.e. niche-based dynamics) and ecological drift (i.e. neutral dynamics governed by demographic stochasticity). However, spatial models of competition rarely consider the joint operation of these two processes. We develop a model based on the original competition-colonization trade-off model that incorporates niche and neutral processes and several realistic facets of ecological dynamics: it allows local competition (i.e. competition within a patch) to occur within communities of a finite size, it allows competitors to vary in the degree of competitive asymmetry, and it includes the role of local migration (i.e. propagule pressure). The model highlights the role of community size, i.e. the number of competitors in the local community, in mediating the relative importance of stochastic and deterministic forces. In metacommunities where local communities are small, ecological drift is substantial enough that strong competitors become effectively neutral, creating abrupt changes in the outcome of competition not predicted by the standard competition-colonization trade-off. Importantly, the model illustrates that, even when other aspects of species interactions (e.g. migration ability, competitive ability) are unchanged, local community size can alter the dynamics of metacommunity persistence. Our work demonstrates that activities which reduce the size of local communities, such as habitat destruction and degradation, effectively compound the extinction debt.
竞争相互作用的结果可能受到竞争优势（即基于生态位的动态）和生态漂变（即由人口随机性控制的中性动态）的共同影响。然而，竞争的空间模型很少考虑这两个过程的联合作用。我们开发了一个基于原始竞争-定居权衡模型的模型，该模型结合了生态位和中性过程以及生态动态的几个现实方面：它允许在有限大小的群落中发生局部竞争（即斑块内的竞争），允许竞争者在竞争不对称程度上有所不同，并且包括局部迁移（即繁殖体压力）的作用。该模型强调了群落大小（即当地群落中的竞争者数量）在调节随机和确定性力量的相对重要性方面的作用。在局部群落较小的复合社区中，生态漂变足够大，以至于强竞争者实际上变得中性，从而导致竞争结果发生突然变化，而这些变化是标准竞争-定居权衡所无法预测的。重要的是，该模型表明，即使其他方面的物种相互作用（例如，迁移能力、竞争能力）保持不变，局部群落大小也可以改变复合社区持续存在的动态。我们的工作表明，减少局部群落大小的活动，如栖息地破坏和退化，实际上会加剧灭绝债务。
