Dissertation Research: Patterns of Genetic Variation in Natural Populations: Chromosomal, Single Gene, and Polygenic

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Understanding the population genetic structure of organisms distributed in discrete populations is essential to understanding the subsequent evolution of such populations. Most studies examine the pattern of genetic variation within and among populations using allozymes, neglecting sources such as chromosomal and morphological variation. These additional sources of variation are expected to contrast with allozyme variation. Random processes such as drift should be important in the spread and/or fixation of chromosomal variants since individuals heterozygous for chromosome arrangements are often observed to have reduced fertility. Selection acting on morphological traits, however, can counteract such random processes. Allozymes, assumed to be neutral genetic markers, will be affected by random processes potentially important in fixation of chromosomal variants. Considering all three sources of variation together, chromosomal variation should coincide more closely with allozyme than with morphological variation. The coPI will examine the within and among population patterns of chromosomal variation in relation to both single gene (allozymes and discrete morphological traits) and polygenic (quantitative genetic) variation in Clarkia dudleyana, a species known to contain chromosomal polymorphism between populations. The coPI will examine the chromosomal relationship, estimate gene frequencies of both allozymes and morphological traits, and examine the pattern of polygenic variation for eight natural populations. The coPI will also study selection to determine whether current selection regimes are consistent with differences in the pattern of morphological variation as compared to allozyme and chromosomal variation. The general significance of the study is that it will improve our understanding of the survival and spread of natural plant populations.