| The study of the process of evolution in a particular organism involves, among many things, a synthesis of information regarding the biology, physiology, and possible selective factors acting on populations, as well as an understanding of the distribution of genetic variation within and among populations. The present work attempts to shed light on the process of evolution and adaptation in asexual populations of the intertidal marine red alga Porphyra umbilicalis Kutzing in the Gulf of Maine. I synthesized information on the biology and physiology of this organism, as well as theoretical work on the evolution of asexual populations (Introduction), then describe the use of a "common garden" experimental design to grow tissue from multiple populations under similar conditions in culture (Chapter 1) to measure simple physiological traits (Chapter 2, 3, 5) in order to understand the distribution of quantitative genetic variation within and among populations. I optimized a method for extracting high quality DNA from this species (Chapter 4), and used genetic markers (microsatellites or EST-SSR loci) to describe the distribution of genetic variation within and among populations (Chapter 5). Finally, I used a hypothesis-independent approach to understand how populations interact with their environment in a typical and atypical habitat, and use these data to formulate hypotheses about the regulation of a particular gene in low and high nitrogen environments (Chapter 6). My work confirmed that genetic variation within and among asexual populations of this species is relatively high, and that the environment is a significant factor influencing gene expression differences among populations. |
