Neale Joseph T, Juliano Steven A
School of Biological Sciences, Illinois State University, Normal, Illinois 61790-4120 USA.
Ecol Entomol. 2021 Feb;46(1):56-65. doi: 10.1111/een.12940. Epub 2020 Sep 18.
Population responses to extrinsic mortality can yield no change in number of survivors (compensation) or an increase in number of survivors (overcompensation) when the population is regulated by negative density-dependence. This intriguing response has been the subject of theoretical studies, but few experiments have explored how the source of extrinsic mortality affects the response. This study tests abilities of three functionally diverse predators, alone and combined, to induce (over)compensation of a prey population. Larval (Diptera: Culicidae) were exposed to predation by (Crustacea: Copepoda) (Diptera: Culicidae) (Diptera: Corethrellidae), all three in a substitutive design, or no predation. The number of survivors to adulthood, female size and development time, and a composite index of performance () were analysed. Predator treatment did not have a significant effect on total number of survivors, nor on number of males, suggesting mortality by predation was compensatory. Predation significantly affected number of female survivors, with a trend of more females produced with predation, though no tests were significant. Predation significantly increased female development rate and relative to no-predator control. A sensitivity analysis indicated that the change in the number of female adults produced was the largest contributing factor to the differences in among cohorts. While predation did not significantly increase overall production of adults, it did release survivors from density-dependent effects sufficiently to increase population performance. This study provides an empirical test of mechanisms by which predation may yield positive effects on a population of victims, a phenomenon predicted to occur across many taxa and food webs.
当种群受到负密度依赖调节时，种群对外源死亡率的反应可能导致存活个体数量不变（补偿）或存活个体数量增加（超补偿）。这种有趣的反应一直是理论研究的主题，但很少有实验探讨外源死亡率的来源如何影响这种反应。本研究测试了三种功能不同的捕食者单独或组合诱导猎物种群（超）补偿的能力。将幼虫（双翅目：蚊科）暴露于（甲壳纲：桡足类）、（双翅目：蚊科）、（双翅目：摇蚊科）的捕食之下，所有三种捕食者采用替代设计，或不进行捕食。分析了成年后的存活数量、雌虫大小和发育时间，以及综合表现指数（）。捕食处理对存活总数和雄虫数量均无显著影响，这表明捕食造成的死亡率具有补偿性。捕食对雌虫存活数量有显著影响，捕食情况下产生更多雌虫呈一种趋势，尽管没有检验达到显著水平。与无捕食者对照相比，捕食显著提高了雌虫发育速率和。敏感性分析表明，产生的成年雌虫数量变化是不同队列间差异最大的影响因素。虽然捕食并没有显著增加成虫的总体产量，但它确实使存活个体充分摆脱了密度依赖效应，从而提高了种群表现。本研究对捕食可能对受害种群产生积极影响的机制进行了实证检验，这种现象预计会在许多分类群和食物网中出现。
