In attempts to understand evolution, the study of genetic variation within and among species has been a major research focus. In some species, genetic variability at biochemical loci is so great the one must ask whether it exists as a result of natural selection or represents random "genetic noise." This research will examine this question by studying: (1) the model organism, Fundulus heteroclitus, (2) representative enzyme systems, and (3) mitochondrial DNA patterns. These studies include: the mechanisms responsible for different enzyme concentrations among populations, the specific genetic changes responsible for known functional alterations in the enzyme lactate dehydrogenase, the study of functional differences in several other enzyme systems, metabolic studies to determine how enzyme variation affects physiology, developmental rate studies to reveal how cellular differences manifest themselves as phenotypic characters, experiments that will assess the magnitude of selection, and mtDNA pattern studies that will provide information on the previous genetic history and population dynamics of the model species. The results of this multidisciplinary approach, which begins at the molecular level and progresses to the ecological level, will lead to a broader understanding of evolution and help answer the hotly debated question: "Does the majority of genetic variation at the molecular level provide the biochemical rootstock of evolutionary change?"
