DISSERTATION RESEARCH: Invasion of Aquatic Habitats as an Evolutionary Process

该项目将进化遗传学和生理生态学方法相结合，为研究物种入侵提供了强有力的手段。 重点是对淡水栖息地的入侵海洋和河口浮游桡足类，Eurytemora affinis。 有两种假说可以解释它对淡水生境的入侵。 淡水定殖是（A）多个独立事件，或（B）罕见事件，随后在相似的栖息地中扩散。 本项目的目标是（1）通过重建殖民历史来验证这些假设，（2）确定栖息地过渡期间生理性状的变化，以及（3）确定栖息地过渡是否通过遗传适应或驯化发生。 利用两个基因的DNA序列构建了12个不同盐度的桡足类种群的系统发育，以确定其定殖的历史和地理途径。 将确定6个种群的耐盐性宽度，然后映射到演替过程中，以确定在生境过渡期间生理性状的变化。 对盐度变化的反应将被测量，以确定栖息地的转变是否涉及种群的遗传适应或个体驯化。 将外来物种引入水生生境是一个重大的环境问题。 这项研究将揭示栖息地过渡的重要过程，并有助于我们了解栖息地入侵，当地的适应，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.