A fundamental problem in the study of marine ecology is to identify natural populations and understand how they change through time. This problem is especially challenging in marine organisms that metamorphose during development or change habitats throughout their life cycle. Adult stages of many species are benthic (e.g. barnacles), while their larval stages are planktonic and may disperse over long distances. Many aspects of the ecology of adult populations of coastal invertebrates have been intensively studied, but the effects of larval dispersal on genetic structure of populations are unclear and potentially extensive. The goal of this fellowship research is to gain knowledge of the degree to which dispersal and selection combine to affect variation between populations. Genetic differences may arise via natural selection, genetic drift, non-random mating, and mutation. Differentiation is reduced by gene-flow between populations: dispersal of propagules such as eggs, sperm, larvae, cysts, or adults. These two forces are usually in a state of flux and the genetic patterns we see at one point in time depend on the relative strengths of these forces. Dr. West will compare individual mitochondrial DNA sequences of planktonic barnacle larvae and newly settled juveniles collected adjacent to adult sites. Differences between these groups and possibly changes within cohorts through time will yield a new perspective on formation and maintenance of the genetic structure of these populations. Mitochondrial DNA analysis can reveal the degree to which larvae travel as clouds of closely related individuals. Continued sampling of these patterns through time gives clues to the amount of genetic fluctuation that a population may naturally experience. The studies are made possible by means of primer-directed enzymatic DNA amplification using the polymerase chain reaction (PCR).
