Non-consumptive predator effects on prey population size: a dearth of evidence,Journal of Animal Ecology

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Non-consumptive predator effects on prey population size: a dearth of evidence
Journal of Animal Ecology ( IF 3.5 ) Pub Date : 2020-04-20 , DOI: 10.1111/1365-2656.13213
Michael J Sheriff ₁ , Scott D Peacor ₂ , Dror Hawlena ₃ , Maria Thaker ₄

Affiliation

There is a large and growing interest in non-consumptive effects of predators. Diverse and extensive evidence shows that predation risk directly influences prey traits, such as behaviour, morphology, and physiology, which in-turn, may cause a reduction in prey fitness components (i.e., growth rate, survival, and reproduction). An intuitive expectation is that non-consumptive effects that reduce prey fitness will extend to alter population growth rate and therefore population size. However, our intensive literature search yielded only 10 studies that examined how predator-induced changes in prey traits translate to changes in prey population size. Further, the scant evidence for risk-induced changes on prey population size have been generated from studies that were performed in very controlled systems (mesocosm and laboratory), which do not have the complexity and feedbacks of natural settings. Thus, although likely that predation risk alone can alter prey population size, there is little direct empirical evidence that demonstrates that it does. There are also clear reasons that risk effects on population size may be much smaller than the responses on phenotype and fitness components that are typically measured, magnifying the need to show, rather than infer, effects on population size. Herein we break down the process of how predation risk influences prey population size into a chain of events (predation risk affects prey traits, which affect prey fitness components and population growth rate, which affect prey population size), and highlight the complexity of each transition. We illustrate how the outcomes of these transitions are not straightforward, and how environmental context strongly dictates the direction and magnitude of effects. Indeed, the high variance in prey responses is reflected in the variance of results reported in the few studies that have empirically quantified risk effects on population size. It is therefore a major challenge to predict population effects given the complexity of how environmental context interacts with predation risk and prey responses. We highlight the critical need to appreciate risk effects at each level in the chain of events, and that changes at one level cannot be assumed to translate into changes in the next because of the interplay between risk, prey responses, and the environment. The gaps in knowledge we illuminate underscore the need for more evidence to substantiate the claim that predation risk effects extend to prey population size. The lacunae we identify should inspire future studies on the impact of predation risk on population-level responses in free-living animals.

中文翻译：

非消耗性捕食者对猎物种群规模的影响：证据不足

人们对捕食者的非消耗性影响越来越感兴趣。多样化和广泛的证据表明，捕食风险直接影响猎物的特征，如行为、形态和生理，这反过来又可能导致猎物健康成分（即生长速度、存活率和繁殖）的降低。一个直观的预期是，降低猎物适应性的非消耗效应将扩展到改变种群增长率，从而改变种群规模。然而，我们密集的文献搜索只产生了 10 项研究，这些研究检查了捕食者引起的猎物特征变化如何转化为猎物种群规模的变化。此外，在非常受控的系统（中宇宙和实验室）中进行的研究中，很少有证据表明猎物种群规模的风险引起的变化，没有自然环境的复杂性和反馈。因此，尽管捕食风险本身可能会改变猎物种群规模，但几乎没有直接的经验证据表明它确实如此。也有明显的原因，风险对种群规模的影响可能远小于通常测量的对表型和适应度组成部分的反应，因此需要显示而不是推断对种群规模的影响。在此，我们将捕食风险如何影响猎物种群规模的过程分解为一系列事件（捕食风险影响猎物特征，影响猎物适应性成分和种群增长率，从而影响猎物种群规模），并强调每次转变的复杂性. 我们说明了这些转变的结果并不简单，以及环境背景如何强烈地决定影响的方向和大小。事实上，猎物反应的高方差反映在少数研究中报告的结果的方差中，这些研究对种群规模的风险影响进行了经验量化。因此，鉴于环境背景如何与捕食风险和猎物反应相互作用的复杂性，预测种群影响是一项重大挑战。我们强调了在事件链中的每个级别评估风险影响的关键需求，并且由于风险、猎物反应和环境之间的相互作用，不能假设一个级别的变化会转化为下一个级别的变化。我们阐明的知识差距强调需要更多证据来证实捕食风险影响扩展到猎物种群规模的说法。

更新日期：2020-04-20

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