Population Dynamics and the evolution of phenotypic plasticity: Experimental Adaptive Dynamics.

动物或植物的生存能力取决于它们应对温度、降雨、捕食者和寄生虫等问题的能力。一些动物和植物能够识别它们生活的栖息地的变化，并相应地改变。这些可能包括动物有多活跃，它们吃了多少，它们生长得有多快，它们有多少后代，甚至它们是如何发育的。例如，当水蚤在有鱼的栖息地长大时，它们会长出头和尾部的刺，这会使鱼更难吃掉它们，但当鱼不在时，这些刺就不会产生。动物根据周围环境改变行为的这种能力被称为表型可塑性。一种动物或植物可以有多大的可塑性？在一个完美的世界里，具有无限可塑性的有机体可能会生活在任何地方。然而，这并不是我们通常所观察到的。大多数动植物的分布在一定程度上受到限制。此外，生活在变化不大的环境中的动植物通常较少使用塑料。其中一个原因可能是，塑料既有好处，也有成本。这项工作旨在研究这些可塑性的成本是什么。在我们能够做到这一点之前，我们首先必须定义什么是塑料动物。这并不像听起来那么容易，因为在任何动物身上，某些特征可能比其他特征更具可塑性。例如，在季节后期孵化的蜻蜓会减小它们的身体尺寸(塑料)，以便总是能够尽可能快地发育(而不是塑料)。目前，我们对某一特征的可塑性与其他特征的可塑性之间的关系知之甚少。这意味着我们必须测量动物在不同环境中改变许多特征的方式，然后才能比较一个有机体和另一个有机体的可塑性。在这个项目的第一部分，我将比较水蚤的不同克隆(具有相同基因的个体)在高食物环境和低食物环境中改变它们的摄食率、生长、繁殖和存活的程度。这将使我能够(1)确定不同特征的塑料反应是如何相互关联的，以及(2)确定某些克隆是否比其他克隆表现出更多的整体可塑性(所有特征)，以响应食物供应的变化。在项目的第二部分，我将测试在某些环境中塑料是昂贵的这一想法。正常情况下，试图衡量一个有机体的特定特征如何影响其在任何环境中的成功都是极其困难的。研究水蚤的好处是它们繁殖得如此之快(10天)，我可以直接与塑料和非塑料克隆在许多世代之间竞争。通过这种方式，一个特定克隆在任何环境中的成功都可以通过它取代另一个克隆的能力来衡量。利用这些种群竞争实验，我将检验塑料克隆能否在可变环境中取代非塑料克隆，以及非塑料克隆能否在恒定环境中取代塑料克隆，就像塑料成本高昂时所预期的那样。

The ability of an animal or plant to survive is dependent on their ability to deal with things like temperature, rainfall, predators and parasites. Some animals and plants are able to recognize changes in the habitat that they live in and change accordingly. These may include things like how active an animal is, how much they eat, how fast they grow, how many offspring they have, or even how they develop. For example, when water fleas grow up in a habitat in which fish are present they develop head and tail spines that make it harder for a fish to eat them, however these spines are not produced when fish are absent. This ability of an animal to change what they do depending upon their surroundings is called phenotypic plasticity. How plastic can an animal or plant be? In a perfect world, an organism that had unlimited plasticity could potentially live anywhere. However, this is not what we generally observe. The distribution of most plants and animals is constrained to some degree. Moreover, plants and animals that live in environments that don't change very much are generally less plastic. One reason for this could be that there are costs of being plastic as well as benefits. This work aims to examine what these costs of plasticity are. Before we can do this, we first have to define what a plastic animal is. This is not as easy as it sounds because in any animal some characteristics may be more plastic than others. For example, dragonflies that hatch late in the season reduce their body size (plastic) in order to always be able to develop as quickly as possible (not plastic). At present we have very little idea how plasticity in one characteristic is related to plasticity in others. This means that we have to measure the way that animals change many characteristics in different environments before we can compare the plasticity of one organism with another. In the first part of this project, I will compare the extent that different clones (individuals with identical genes) of a water flea change their feeding rate, growth, reproduction and survival in high and low food environments. This will enable me to (1) determine how plastic responses in different characteristics are related to each other, and (2) determine whether some clones show more overall plasticity (all characteristics) than others in response to a change in food availability. In the second part of the project, I will test the idea that being plastic is costly in some environments. Normally trying to measure how a particular characteristic of an organism influences its success in any environment is extremely difficult. The advantage of studying water fleas is that they reproduce so quickly (10 days) I can directly compete plastic and non-plastic clones against each other over many generations. In this way, the success of a particular clone in any environment can be measured as its ability to replace another clone. Using these sorts of population competition experiments I will examine whether plastic clones can replace non-plastic clones in a variable environment and whether non-plastic clones can replace plastic clones in a constant environment as would be expected if being plastic is costly.