Mitochondrial DNA (mtDNA) is an extra-nuclear, maternally inherited set of genes assumed to be selectively neutral; that is, their distribution within populations is subject only to chance events, and not to differences in evolutionary fitness conferred by these genes. The goal of this project is to detect effects, if any, of mitochondrial genes on an organism's morphology or nuclear genetic makeup. This is a first step towards understanding how mitochondrial and nuclear gene interactions may affect development, and , thus, how mtDNA genotypes may be subject to evolution by natural selection. Populations of wild trout, known to be hybrids between evolutionarily divergent groups, will be studied. Randomly mating hybrid swarms formed from such distinct taxa are rare in nature. They will permit statistical tests for association between mtDNA genotype and nuclear genotype, sex, and morphology (number of vertebrae, fluctuating asymmetry, etc.). Demonstration that mtDNA is subject to natural selection would have important implications for the widespread use of mtDNA as a marker for studies of genetic variation and population structure. Also, wild populations of trout are an important natural resource, the integrity of which is seriously threatened by hybridization with introduced species. This study will add to our understanding of the dynamics of interspecies hybridization in salmonid fishes.
