Optimal investment in costly anti-predator defences

他的申请描述了对几乎所有生态学的一个主要特征的第一个综合理论-实证研究：即排斥反捕食者防御。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水平。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。尽管在理解反捕食者防御的机制功能方面已经取得了很大的进步，但在这里，我们采取了更生态的观点，试图探索是否可以在物种内部和物种之间的这种防御程度的变化中看到一般趋势。这就需要把对防御有效性的认识与对其成本的考虑结合起来。特别是，我们将重点关注毒素和其他化学防御在分类学和生态学上广泛存在的情况。化学防御在变温动物中特别普遍，并从机械和生理的角度进行了深入研究。此外，从分类学和地理上考虑了这种防御的分布。然而，目前还没有关于驱避反捕食者防御的最佳投资水平的预测理论，在该理论中可以解释这种经验推导的模式。这与强烈的理论关注形成鲜明对比，理论关注集中在“警示”信号的进化和维持上，这些信号可以警告潜在的捕食者这种化学防御。然而，现有的警告理论无法预测最佳二级防御水平的变化，因为该理论以一种简单的方式将这种防御视为不受选择影响的固定特征。先前有少数研究试图确定对构成次级防御的最佳投资，含蓄地假设尽管化学防御在未成熟的生活史阶段起到减少捕食的作用，但这种防御的生理成本只表现为成虫阶段繁殖力的降低。然而，有大量的经验证据表明，毒素的获取可以减缓幼鱼的生长速度。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生存的机会，但可能会通过减缓生长速度来增加受到攻击的风险，从而增加成熟的时间。最优防御的数学处理忽略了这种权衡，这极大地限制了这些模型在分类学上的适用性。因此，这种权衡是我们提出的研究的核心。因此，这个项目的目的是：1。提供第一个反捕食者防御投资的一般预测理论，以及这种投资如何随着个体发生、生活史和生态而变化。2. 使用现有的经验关系和目的设计的实验来参数化这个模型。3. 使用这个模型来预测国防投资在不同的生态环境、生活史战略和发展阶段应该如何变化。4. 使用现有和目的收集的比较数据评估这些预测。具体而言，我们将构建状态相关的动态规划模型来探讨以下五个问题：a)外部生态对国防投资的影响b)生活史与国防投资之间的关系c)活动、微生境开发与国防投资之间的关系d)毒素的隔离与合成的进化生态学e)国防投资与本体颜色变化之间的关系这一理论发展将得到有目的的设计实验的支持，这些实验旨在参数化评估和验证模型假设，并通过旨在测试模型预测的比较分析。

his 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.