ADAPTATION AND PLASTICITY IN NEST CONSTRUCTION: BEHAVIOURAL AND MOLECULAR FACTORS AFFECTING DESIGN IN AN EXTENDED PHENOTYPIC TRAIT

从无脊椎动物到鸟类，筑巢是许多动物繁殖行为的重要组成部分。父母建造巢穴作为卵和发育后代的容器，它们的设计对它们的功效有重要的影响。巢和其他动物结构被描述为扩展表型特征/体外特征，但反映了建造者的基因型。因此，我们可以预期，生活在不同环境中的同一物种的种群会进化出不同的筑巢结构，这一过程被称为“适应性分化”。然而，正如传统特征是基因和环境相互作用的结果一样，动物建造结构的设计也受到外部因素的影响。个体在面对环境变化时调整行为模式的能力被描述为“表型可塑性”。在这个项目中，我们将研究三棘棘鱼筑巢行为的适应性差异和表型可塑性。雄性刺鱼筑巢，为求爱提供了场所，也为雌性刺鱼产卵提供了场所。我们选择棘鱼是因为：(1)它们自然占据并筑巢于各种水生栖息地，从静止的池塘到湍急的溪流；(2)它们非常适合实验室研究，因此我们对它们的生殖行为生态学已经有了很多了解；(3)它们的基因组最近已被测序，这使我们能够询问个体如何在分子和行为水平上调整筑巢。我们将利用不同种群的棘鱼进行一系列实验，提出4个相关且重要的问题；有些从河流中进化而来，有些从湖泊中进化而来。首先，我们将研究在筑巢过程中如何经历流动状态，以及可用材料的类型，相互作用以确定巢的设计。然后，我们将允许雄性在一种状态（“静止”或“流动”）下筑巢，然后测试其在建造状态和相反状态下的性能方面（包括对高流速的抵抗力，对低氧水平的敏感性以及对雌性的吸引力）。这将量化建造一个不适合当前流动条件的巢的成本。然后，我们将检查雄性在环境变化时能够在多大程度上调整筑巢行为，通过检查第一种情况下个体雄性的筑巢行为和巢设计，然后是交替的流动状态。雄性刺鱼分泌一种叫做Spiggin的“胶水”，用来将筑巢材料粘在一起，并将它们固定在基质上。最近的研究已经确定了肾脏中负责斯皮金合成的基因。我们想知道雄性棘鱼是否可以通过改变Spiggin基因的表达来调节Spiggin的产生，以应对流动条件的变化。这可能使雄性可以根据流量的变化直接调整巢的强度。因此，我们将从不同的人群中收集雄性，也从控制流动制度下的雄性实验中收集雄性，并进行分析，允许定量肾脏中基因产物的数量（而不仅仅是它的存在/不存在）。我们的研究将是第一个研究适应分化和表型可塑性在动物构建行为中的相对作用的研究，并且在结合行为和分子方法方面是独一无二的。我们的研究结果将表明，鱼类的筑巢行为在多大程度上适应了当地的环境，以及它们在条件变化时能在多大程度上调整筑巢模式。了解行为可塑性的程度和局限性是很重要的，因为它将帮助我们预测物种引入和全球气候变化如何可能影响个体和种群的成功。

Nest building is an essential component of reproductive behaviour in many animals, from invertebrates to birds. Parents construct nests as receptacles for eggs and developing offspring, and their design has important implications for their efficacy. Nests and other animal constructions have been described as extended phenotypic traits / extra-body characteristics that nonetheless reflect the genotype of the builder. Hence, we might expect populations of a species living in different environments to have evolved different nest construction, a process called 'adaptive divergence'. However, just as conventional traits result from the interaction of genes and environment, so the design of animal built structures is shaped by external factors. The ability of individuals to adjust patterns of behaviour beneficially when faced with environmental change is described as 'phenotypic plasticity'. In this project, we will investigate adaptive divergence and phenotypic plasticity in the nest building behaviour of a fish, the 3-spined stickleback. Male sticklebacks build nests, which provide a focus for courtship and a place for females to lay eggs. We chose sticklebacks because (1) they naturally occupy, and build nests in, a wide range of aquatic habitats, from static ponds to fast flowing streams; (2) they are extremely well suited to laboratory studies, so we already know a great deal about their reproductive behavioural ecology; and (3) their genome has recently been sequenced, allowing us to ask questions about how individuals adjust nest building at molecular, as well as behavioural, levels. We will undertake a series of experiments to ask 4 related and important questions, using sticklebacks from different populations; some that have evolved in rivers, and some from lakes. First, we will examine how the flow regime experienced during nest building, and the type of materials available, interact to determine the design of nests. We will then allow males to build nests under one regime ('still' or 'flow') before testing aspects of its performance (including resistance to high flow rates, susceptibility to low oxygen levels, and attractiveness to females) under the regime in which it was built, and under the opposite regime. This will quantify the costs of building a nest that is unsuited to prevailing flow conditions. We will then examine to what extent males are able to adjust nest building behaviour when environments change, by examining building behaviour and nest design of individual males under first one, and then the alternate, flow regime. Male sticklebacks secrete a 'glue', Spiggin, which used to stick nesting materials together and anchor them to the substratum. Recent research has identified the genes responsible for Spiggin synthesis in the kidney. We want to know if male sticklebacks can regulate the production of Spiggin in response to changing flow conditions by altering the expression of Spiggin genes. This might allow males to adjust nest strength in direct response to changing flow rates. We will therefore collect males from the different populations, and also from experiments in which males are held under controlled flow regimes, and undertake an analysis that allows the amount of gene product (rather than just it presence/absence) in the kidney to be quantified. Our study will be among the first to examine the relative roles of adaptive divergence and phenotypic plasticity in animal construction behaviour, and is unique in incorporating both a behavioural and molecular approach. Our results will show to what extent the nest building behaviour of fish is adapted to their local environment, and to what extent they can adjust patterns of construction when conditions change. Understanding the extent and limitations of behavioural plasticity is important because, for example, it will help us predict how species introductions and global climate change are likely to affect success of individuals and of populations.