Collaborative Research: Effects of Herbivory and Stress on Seaweed Resource Acquisition, Allocation Patterns, and Fitness

威廉姆斯这项研究将调查一种生态上重要的潮间带岩藻(Fucus Gardneri)如何分配资源，以响应两个关键环境变量的变化，即草食和干燥压力(如潮间带经历的高度干旱压力)。这些变量通常是独立研究的，但它们对海藻的综合影响在自然界中必须是重要的。藻类必须就如何将获取的能量分配给生长、繁殖、威慑(例如，抗食草动物化学物质)和其他关键的生活史功能做出“决定”，特别是在压力降低资源获取能力的情况下。虽然陆生植物的资源分配模式正在被深入研究，但对于藻类几乎没有类似的工作，尽管它们易于操纵，数量丰富，与维管植物的系统发育形成了有趣的对比，并且在近岸海洋生态系统中发挥着重要作用。此外，对于分配模式对海藻健康的影响，人们几乎一无所知。这里的适合度表示为有限的人口增长率。将生理学与健康联系起来是至关重要的，因为生长甚至繁殖的变化可能不会转化为对海藻种群的影响。在这个项目中，将首先开发一个简单的模型，以平衡资源获取(作为净初级生产量)和所有已知的岩藻类主要资源分配汇(生长、繁殖、邻氯单宁、储存、渗出、对食草动物的损失)。这个模型将提供一种工具来比较在田间和在中胚层中操纵时，Fucus对胁迫和食草性梯度的生理反应。研究将涉及：1)观察岩藻的野外种群，以量化它们在草食和胁迫的自然梯度上的分配模式的变化；2)在实验室的净初级生产力(浮现和浸泡)以及田间生长菌体模型的其他术语的实验室中进行生理测量；3)在田间和实验室中操纵应激(出现时间、干燥)和草食的关键变量，其中在这些条件下藻体将被提高到繁殖大小，然后将评估它们的分配模式；以及4)建立人口模型，根据在应激和草食的潮间带梯度中在Talli测量的生活史转变来估计种群增长率。还将对被认为含有抗草食化合物的提取物的化学成分和威慑力进行初步研究。该方法旨在评估涉及潮间带海藻种群资源分配及其后果的几个具体问题，这些海藻种群具有比海藻对压力和草食的反应更广泛的影响。尽管几乎所有以前关于生物体内资源分配的研究都假设资源获取是恒定的，但这个项目将用净初级生产量的测量来检验这一假设。在压力条件下，净初级生产力假设会在潮间带梯度上有所不同。如果假设为假，如果不考虑资源获取的差异，分配权衡比较将是无效的。它还假设存在一个临界压力水平，超过这个水平就不可能在资源汇之间重新分配。重新分配资源的能力受到生理限制的问题很少得到解决。最后，在成年生物体中展示的分配模式通常被认为代表健康或适应的一个重要方面。然而，成虫阶段可能不是对种群增长率和种群持久性做出贡献的最重要的生活史阶段。人口模型的敏感性/弹性分析将确定哪些生活史转变(例如，成虫存活和繁殖与补充)对种群增长率最关键，从而确定成虫内的分配模式对海藻种群增长是否重要。。-这项研究将为海藻的资源分配问题提供第一个综合办法，并将证明环境严酷程度(生物或非生物)在多大程度上反映在藻类的表现中。通过这种方式，它将在物理变化(例如在全球变暖期间可能发生的变化)与藻类个体生长和繁殖的能力以及海藻种群的持续存在之间建立联系。

Williams This research will investigate how an ecologically important intertidal fucoid alga (Fucus gardneri) allocates resources in response to variation in two key environmental variables, herbivory and desiccation stress (such as that experienced high in the intertidal zone). These variables are typically studied independently, yet it is their combined effect on seaweeds that must be important in nature. Algae must make "decisions" about how to allocate acquired energy to growth, reproduction, deterrency (e.g., anti-herbivore chemicals), and other key life-history functions, particularly when stress reduces resource acquisition capacity. While resource allocation patterns are being investigated intensively in terrestrial plants, almost no comparable work exists for algae, despite their ease of manipulation, abundance, interesting phylogenetic contrast to vascular plants, and important roles in nearshore marine ecosystems. In addition, virtually nothing is known about the consequences of allocation patterns to seaweed fitness. Fitness here is represented as the finite rate of population growth. Linking physiology to fitness is critical because changes in growth, or even reproduction, may not translate to effects on seaweed populations. In this project, a simple model that balances resource acquisition will be developed first (as Net Primary Production) against all known major resource allocation sinks for fucoids (growth, reproduction, phlorotannins, storage, exudation, loss to herbivores). This model will provide a tool to compare the physiological response of Fucus to gradients in stress and herbivory in the field and when manipulated in mesocosms. The research will involve: 1) observations of field populations of fucoids to quantify variation in their allocation patterns across natural gradients in herbivory and stress; 2) physiological measurements in the laboratory of Net Primary Production (emersed and immersed) and the other terms of the model for field-grown thalli; 3) manipulation both in the field and in laboratory mesocosms of the key variables of stress (emersion time, desiccation) and herbivory where thalli will be raised to reproductive size under these conditions, and then their allocation patterns will be assessed; and 4) development of demographic models to estimate population growth rates from life-history transitions measured in thalli across an intertidal gradient in stress and herbivory. Preliminary studies of the chemical composition and deterrency of extracts thought to contain anti-herbivore compounds will also be performed.The approach is designed to evaluate several specific issues involving resource allocation in, and its consequences for, intertidal seaweed populations that have broader implications than the response of seaweeds to stress and herbivory. Although virtually all previous studies of resource allocation in organisms assume that resource acquisition is constant, this project will test this assumption with measurements of Net Primary Production. Net Primary Production hypothetically varies across intertidal gradients in stressful conditions. If the assumption is false, allocation trade-off comparisons would not be valid without accounting for variation in resource acquisition. It is also hypothesized that there is a critical stress level above which reallocation among resource sinks is not possible. A physiological limit to the capacity to reallocate resources has rarely been addressed. Finally, allocation patterns demonstrated in adult organisms often are assumed to represent an important aspect of fitness or adaptedness. Yet, the adult phase might not be the most important life history stage in contributing to the population growth rate, and thus persistence of the populations. Sensitivity/elasticity analyses of the demographic models will determine which life history transitions (e.g., adult survival and reproduction versus recruitment) are most critical to the population growth rate, and thus, if allocation patterns within adults are important to seaweed population growth. . - This research will provide the first integrated approach to questions of resource allocation in seaweeds, and will demonstrate to what extent environmental harshness (biotic or abiotic) is reflected in algal performance. In this way, it will provide a link between physical changes (such as might occur during global warming) and the ability of algal individuals to grow and reproduce and seaweed populations to persist.