Fox Jeremy W
Department of Biological Sciences, University of Calgary, 2500 University Drive NW, Calgary, Alberta T2N 1N4, Canada.
Am Nat. 2007 Sep;170(3):396-408. doi: 10.1086/519855. Epub 2007 Jul 19.
Dispersal among sites can affect within-site competitive outcomes via source-sink dynamics. Source-sink dynamics are thought to affect competitive outcomes primarily via spatial subsidies: by redistributing individuals from sources to sinks, source-sink dynamics can alter competitive outcomes in both sources and sinks. However, dispersal also can affect competitive outcomes via demography modification, which occurs when dispersal alters the parameters governing species' per capita demographic rates. For instance, dispersal of exploitative competitors might cause extinction of some of the resources for which competition occurs, thereby altering the competition coefficients. I used protist microcosms as a model system to test whether spatial subsidies alone could explain the effects of source-sink dynamics on competitive outcomes. I examined the long-term outcome of exploitative competition among three bacterivorous ciliate protists in microcosms of high enrichment (sources) and low enrichment (sinks) in both the presence and the absence of dispersal. Dispersal altered competitive outcomes. Fitting mathematical models to the population dynamics revealed that spatial subsidies were insufficient to account for the effects of dispersal. Fitting alternative models strongly suggested that demography modification was an important determinant of competitive outcomes. These results provide the first evidence that dispersal does not simply redistribute competitors but can alter their per capita demographic rates.
不同地点间的扩散可通过源 - 汇动态影响同一地点内的竞争结果。源 - 汇动态被认为主要通过空间补贴来影响竞争结果：通过将个体从源地重新分配到汇地，源 - 汇动态可以改变源地和汇地的竞争结果。然而，扩散也可以通过改变种群统计学特征来影响竞争结果，当扩散改变了控制物种人均种群统计学速率的参数时，就会出现这种情况。例如，掠夺性竞争者的扩散可能会导致一些竞争所针对的资源灭绝，从而改变竞争系数。我使用原生生物微观系统作为模型系统，来测试是否仅空间补贴就能解释源 - 汇动态对竞争结果的影响。我研究了在高富集（源地）和低富集（汇地）的微观环境中，三种噬菌性纤毛虫原生生物在有扩散和无扩散情况下进行掠夺性竞争的长期结果。扩散改变了竞争结果。将数学模型拟合到种群动态中发现，空间补贴不足以解释扩散的影响。拟合其他模型强烈表明，改变种群统计学特征是竞争结果的一个重要决定因素。这些结果首次证明，扩散不仅仅是重新分配竞争者，还可以改变它们的人均种群统计学速率。
