Dissertation Research: Ecological Determinants and Evolutionary Consequences of Dispersal

大多数自然种群表现出生长和衰退的周期。此外，一个特定物种的个体数量可能在一个地区增加，而在邻近地区减少。这些局部动态是由个体在其一生中从一个种群迁移到另一个种群（即分散）联系在一起的。这个研究项目集中在动物传播的两个方面。首先，扩散为物种消失的地区提供了移民，从而补偿了通常发生在许多物种身上的小范围灭绝，并确保了长期的持久性。此外，扩散形成了基因流动的基础，而基因流动是决定种群遗传结构的关键因素之一。以下问题将得到解决。1)假设这种策略会显著影响动物的生存和繁殖机会，那么动物在特定情况下分散的频率应该是多少？2)在这个局部灭绝和再殖民化网络中，哪些关键因素可能引发大规模灭绝？在这样一个相互联系的种群系统中，能够维持多少遗传变异，从而为进化变化提供原料？首席研究员将通过对比计算机模拟和对池塘水甲虫的实地研究来解决这些问题。这些甲虫从一个池塘移动到另一个池塘的速度将在现场测量，研究群体之间的遗传差异将通过分析线粒体DNA变异来量化。这种分子技术是描述动物小范围遗传变异的有力工具。在现场获得的信息将用于检查模拟所基于的假设。然后，计算机模型可以用来推断出这个特定的自然系统之外的情况，以探索在更广泛的条件下扩散的后果。

Most natural populations exhibit cycles of growth and decline. In addition, the number of individuals of a given species may increase in one area while it is decreasing in a neighboring locale. These local dynamics are tied together by individuals that move from one population to another, i.e. disperse, over the course of their lifetime. This research project focuses on two particular aspects of dispersal in animals. First, dispersal provides immigrants to areas from which a species has disappeared thus compensating for small scale extinctions which commonly occur in many species and ensuring long term persistence. Moreover, dispersal forms the basis for gene flow, one of the key factors that determine the genetic structure of populations. The following questions will be addressed. 1) How frequently should animals disperse in a given situation assuming that this strategy significantly influences their chances of survival and reproduction? 2) What are the critical factors that could trigger large scale extinction in this network of local extinction and recolonization? 3) How much genetic variation can be maintained in such a system of interconnected populations thereby providing the raw material for evolutionary change? The principal investigator will approach these questions by contrasting a computer simulation with a field study on the pond- dwelling water beetle Dineutus assimilis. The rate at which these beetles move from pond to pond will be measured in the field and genetic differences among the study populations will be quantified by analyzing mitochondrial DNA variants. This molecular technique is a powerful tool to describe small scale genetic variation in animals. The information obtained in the field will be used to check the assumptions on which the simulation is based. The computer model can then be used to extrapolate beyond this particular natural system to explore the consequences of dispersal over a wider range of conditions.