Dissertation Research: Cascades of Character Change and Speciation in Alaskan Threespine Stickleback

生物学家面临的一个基本挑战是确定生物多样性产生的过程。 适应性辐射是生物多样性的一个主要来源，它通过一系列迅速的物种形成事件产生具有不同生态重要特征的生物。 因此，探索物种形成机制可以为生物多样性的形成过程提供很好的见解。为了研究物种形成，我们将使用三刺鱼的显著适应性辐射，Gasterosteus aculeatus。 在最近的冰川消融地区，例如我们在阿拉斯加的研究地点，淡水刺鱼种群在很短的时间内就从一个共同的海洋祖先中分化出来。 淡水种群已经进化出许多不同类型的生物特征，并且经常在这些特征中显示出相关的分歧。 我们将研究一个特征的变化如何为其他特征的变化奠定基础，这一过程被称为“特征”或“性格级联”。 具体来说，我们将研究棘鱼生态的初始分歧是否会导致一连串的性格变化，最终导致交配偏好的分歧，这是物种形成的第一步。 由于在最近形成的种群中，许多性状的相关进化，三棘鱼为研究性状变化的级联如何导致新物种的形成提供了一个模型系统。

Foster9801378One of the fundamental challenges facing biologists is to define the processes by which biodiversity is created. Adaptive radiations, which occur through a rapid series of speciation events that produce organisms differing in ecologically important traits, are a primary source of biodiversity. Exploration of speciation mechanisms can therefore provide great insight into the processes by which biodiversity is created. To examine speciation we will be using the remarkable adaptive radiation of the threespine stickleback, Gasterosteus aculeatus. In recently de-glaciated areas, such as our research site in Alaska, freshwater stickleback populations have diverged from a common marine ancestor in a remarkably short period of time. The freshwater populations have evolved many different types of organismal traits, and often show a correlated divergence in those traits. We will investigate how change in one trait can set the stage for changes in other traits, a process known as a 'trait' or 'character cascade'. Specifically, we will examine whether an initial divergence in stickleback ecology can cause a cascade of character changes that eventually leads to a divergence in mating preferences, an initial step in speciation. Because of the correlated evolution of many characters in recently formed populations, threespine stickleback provide a model system for studying how cascades of character change can lead to the formation of new species.