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Optimal investment in costly anti-predator defences

对昂贵的反捕食者防御的最佳投资

基本信息

批准号：
NE/E016626/1
负责人：
Graeme Ruxton
金额：
$ 35.11万
依托单位：
University of Glasgow
依托单位国家：
英国
项目类别：
Research Grant
财政年份：
2008
资助国家：
英国
起止时间：
2008 至无数据
项目状态：
已结题

来源：
https://gtr.ukri.org/projects?ref=NE%2FE016626%2F1
关键词：
Optimal investment costly anti predator

项目摘要

This application describes the first integrated theoretical-empirical study of a major feature of almost all ecologies: namely repellent anti-predator defences. Predation is a fundamental process in the structuring of ecological communities, allowing energy flow from primary producers to higher trophic levels. Predation, and the need of potential prey to avoid attack, is also one of the most pervasive causes of co-evolution in ecological communities. Although great strides have been made in understanding the mechanistic functioning of anti-predator defences, here we take a more ecological view, seeking to explore whether general trends can be seen in variation in the extent of such defences within and among species. This requires integration of knowledge of the effectiveness of defences with consideration of their costs. In particular, we will focus on the taxonomically and ecologically widespread case of toxins and other chemical defences. Chemical defences are particularly common among ectotherms and have been intensively studied from a mechanistic and physiological viewpoint. Further, the distribution of such defences have been considered both taxonomically and geographically. However, there is currently no predictive theory on optimal levels of investment in repellent anti-predator defences, within which such empirically-derived patterns can be interpreted. This stands in contrast to the intense theoretical attention that has focussed on the evolution and maintenance of 'aposematic' signals that can warn potential predators of such chemical defences. However, existing aposematism theory can make no predictions about variation in optimal levels of secondary defences since this theory treats such defences in a simplistic manner as fixed traits that are not subject to selection. The small number of previous works that have sought to determine optimal investment in constitutive secondary defences implicitly assume that although chemical defences act to reduce predation in immature life-history stages, the physiological cost of such defences is only manifest as reduced fecundity in the adult stage. However, there is abundant empirical evidence that acquisition of toxins can slow juvenile growth rates. Hence, the key trade-off is ecological: in that investment in defence increases the chance of surviving an attack, but may increase exposure to attacks by slowing growth rate and so increasing time to maturity. The fact that mathematical treatments of optimal defences have ignored this trade-off greatly limits the taxonomic applicability of these models. Hence, this trade-off lies at the heart of our proposed study. Thus, the aims of this project are to: 1. Provide the first general predictive theory of investment in anti-predator defences, and how this changes with ontogeny, life history and ecology. 2. Parameterise this model using existing empirical relationships and purpose designed experiments. 3. Use this model to make predictions about how investment in defence should change for different ecological situations, life-history strategies and developmental stages. 4. Evaluate these predictions using existing and purpose-collected comparative data. Specifically we will construct state-dependent dynamic programming models to explore the following five issues: a) the effects of external ecology on investment in defence b) the relation between life-history and investment in defence c) the relationship between activity, microhabitat exploitation and investment in defence d) the evolutionary ecology of sequestering versus synthesising of toxins e) the relation between investment in defence and ontogenic colour change This theoretical development will be supported by purposed designed experiments design to parameterise, evaluate and validate model assumptions, and by comparative analysis aimed at testing model predictions.

该应用程序描述了几乎所有生态学的一个主要特征的第一个综合理论-经验研究：即排斥性反捕食者防御。捕食是生态群落结构的一个基本过程，使能量从初级生产者流向更高的营养级。捕食，以及潜在猎物避免攻击的需要，也是生态群落共同进化的最普遍原因之一。虽然已经取得了很大的进步，在了解反捕食者防御机制的功能，在这里，我们采取一个更生态的观点，寻求探索是否可以看到一般趋势的变化，这种防御的程度内和物种之间。这就需要将对防御有效性的了解与对防御费用的考虑结合起来。特别是，我们将集中在分类和生态广泛的情况下，毒素和其他化学防御。化学防御在外温动物中特别常见，并且已经从机理和生理学的角度进行了深入的研究。此外，还从分类学和地理学两方面考虑了这种防御的分布情况。然而，目前还没有预测理论的最佳水平的投资，在排斥性的反捕食者防御，在其中这样的衍生模式可以解释。这与集中在进化和维持“警戒”信号的强烈理论关注形成鲜明对比，这些信号可以警告潜在的捕食者这种化学防御。然而，现有的警戒主义理论不能预测二级防御的最佳水平的变化，因为这种理论以简单的方式将这种防御视为不受选择的固定性状。少数以前的作品，试图确定最佳的投资构成二级防御隐含的假设，虽然化学防御的行为，以减少捕食在不成熟的生活史阶段，这种防御的生理成本只表现为在成年阶段的繁殖力降低。然而，有大量的经验证据表明，毒素的收购可以减缓青少年的生长速度。因此，关键的权衡是生态方面的：在防御方面的投资增加了在攻击中幸存的机会，但可能会因增长率放缓而增加遭受攻击的风险，从而增加成熟的时间。事实上，数学处理的最佳防御忽略了这种权衡，大大限制了这些模型的分类适用性。因此，这种权衡是我们拟议研究的核心。因此，本项目的目标是：1。提供第一个一般预测理论的投资，在反捕食防御，以及如何改变这与个体发育，生活史和生态。2.使用现有的经验关系和目的设计的实验参数化这个模型。3.使用这个模型来预测防御投资应该如何改变不同的生态状况，生活史策略和发展阶段。4.使用现有的和专门收集的比较数据来评估这些预测。具体来说，我们将构建状态依赖动态规划模型来探讨以下五个问题：a）外部生态对防御投资的影响B）生活史与防御投资之间的关系c）活动与防御投资之间的关系，微生境开发和防御投资d）毒素螯合与合成的进化生态学e）防御投资和个体发生的颜色变化之间的关系这一理论的发展将得到支持的目的设计的实验设计参数化，评估和验证模型假设，并通过比较分析，旨在测试模型的预测。