DISSERTATION RESEARCH: Invasion of Aquatic Habitats as an Evolutionary Process

该项目结合了进化遗传学和生理生态学的方法，为研究物种入侵提供了一种强有力的方法。重点是海洋和河口浮游桡足类Eurytemora affinis对淡水栖息地的入侵。两种不同的假设可以解释它入侵淡水栖息地的原因。淡水殖民是(A)多个独立事件，或(B)罕见事件，然后在相似的生境中扩散。该项目的目标是(1)通过重建殖民历史来检验这些假说，(2)确定栖息地转变过程中生理特征的变化，以及(3)确定栖息地转变是通过遗传适应还是通过驯化发生的。通过使用两个基因的DNA序列构建来自不同盐度的12个桡足类种群的系统发育图，将确定殖民的历史和地理路径。将确定6个种群的耐盐性广度，然后将其映射到系统发育图上，以确定在栖息地转变期间生理特征是如何变化的。将测量对盐度变化的反应，以确定栖息地的转变是否涉及种群的遗传适应或个人适应。将外来物种引入水生栖息地是一个主要的环境问题。这项研究将揭示栖息地转变过程中的重要过程，并有助于我们理解栖息地入侵、局部适应以及种内遗传和生理多样性。

This project uses a powerful approach for studying species invasion by combining methods of evolutionary genetics and physiological ecology. The focus is on the invasion of freshwater habitats by a marine and estuarine planktonic copepod, Eurytemora affinis. Two alternative hypotheses could account for its invasion of freshwater habitats. Freshwater colonizations have been (A) multiple independent events, or (B) rare events followed by dispersal among similar habitats. The goals of this project are (1) to test these hypotheses by reconstructing the history of colonization, (2) to determine changes in physiological traits during habitat transitions, and (3) to determine whether habitat transitions occur through genetic adaptation or acclimation. The history and geographic pathway of colonization will be determined by constructing a phylogeny of 12 populations of copepods from different salinities using DNA sequences from two genes. Breadth of salinity tolerance will be determined for 6 populations, then mapped onto the phylogeny to determine how physiological traits change during habitat transitions. Response to changes in salinity will be measured to determine whether habitat transitions involve genetic adaptation of populations or individual acclimation. The introduction of exotic species into aquatic habitats is an issue of major environmental concern. This research will reveal important processes involved in habitat transitions, and contribute to our understanding of habitat invasions, local adaptation, as well as intraspecific genetic and physiological diversity.