Collaborative Research: Evolutionary Dynamics of a Color Polymorphism in the Desert Annual Linanthus parryae

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One of the goals of modern evolutionary biology is to understand the forces that determine the distribution and maintenance of genetic variation in natural populations. Two of the primary evolutionary forces are 1) genetic drift, the change in gene frequency due to random processes associated with small population size, and 2) natural selection, the differential survival and reproduction of individuals. The purpose of the proposed research is to quantify the relative importance of these forces in populations of the desert plant, Linanthus parryae. This species flowers after winter rains, and individuals produce either white or blue flowers. Previous research by Dr. Sewall Wright, one of the founders of the field of population genetics, suggested that the population size of this species was quite small, and that the two flower colors were maintained in natural populations by random genetic drift. The alternative hypothesis is that different colored plants are adapted to different local conditions, perhaps due to contrasting abilities to attract pollinators and produce seed. Because flower color is an inherited trait, this selective process will cause a change in the genetic make-up of the population. The proposed research will identify how random events and selective differences between individuals can contribute to evolutionary changes in plant populations. Such information is vital to our understanding of biological diversity.