9520774 Milligan Effective population size determines the rate of change in populations due to a wide range of evolutionary forces. These forces include random genetic drift, natural selection and migration. Accurate estimation of effective size is central to a wide range of questions in evolutionary biology. The best way to make accurate estimates of effective size is to include as much relevant biological information in the estimation process. Many studies have included such information; nevertheless, important aspects still have been neglected. A large number of plants possess the ability to produce some or all of their offspring by self-fertilization. Little is known about the effect of self-fertilization in determining effective population size. This research will use a combination of theoretical population genetics, molecular population genetics, and demography to test the importance of selfing rate in determining the effective population size. Information on selfing rate and demography will be used to develop an estimator of effective size. This estimator will be compared to a long-term historical estimate of effective size based on DNA sequences. These two independent estimates will then be compared. A complex of herbaceous perennial plants in the genus Aquilegia, found in the southwestern United States and adjoining Mexico, will provide the experimental system. This system is well suited to answering this particular question because Aquilegia populations in this region are located in well isolated and well delineated mesic areas. These features make determining population sizes and other demographic parameters feasible. In addition, many of the molecular techniques required for this study have been optimized to work in the Aquilegia system. This research is significant in at least five ways. First, it will lead to the development of theory pertaining to the evolution of a very large group of perennial plant populations. Second, it will test this theory using an ind ependent, long-term, estimate of effective size. Third, the two major datasets developed, a two-year demographic dataset and a molecular population genetic dataset, will be useful for a wide range of evolutionary studies not directly addressed by this research. Fourth, because effective population size is important in the evolution of small populations, this research will provide information that may be required by conservation biologists in making successful management choices. Finally, because this research will provide both current and long-term estimates of effective size, it may be used to examine how populations have changed over time.
