The great Russian geneticist, Theodosius Dobzhansky, once said that "nothing makes sense in biology except in the light of evolution." This statement emphasizes the central relationship of evolution to all the other subdisciplines of the biological scien ces. Because of this central relationship, evolutionary approaches can be applied to a diverse array of biological problems. The work in my laboratory is concerned with these diverse applications of evolutionary biology and is not focused upon a particu lar organism or system.
One common evolutionary approach is the measured genotype approach to the study of complex phenotypes. Because many genes have a known biochemical function, it often is possible to identify candidate loci that may directly influence some phenotype of int erest. Genetic variability at these loci is surveyed molecularly and tested for pheotypic associations. We have used this approach to study molecular variants in the ribosomal DNA of Drosophila mercatorum that trigger a cascade of developmental a nd physiological effects that greatly alter the life history of the fly. Field studies in Hawaii have then revealed the environmental circumstances under which these altered life histories are favored by natural selection. Another application of this sa me approach is a study of the role of lipid metabolic genes in coronary artery ideas in humans. We have successfully related many molecular variants to clinically significant phenotypes and have shown that different genotypes respond very differently to environmental factors such as diet, drugs, or smoking. A third application is a study of the role of evolutionary change in the envelope gene of the HIV virus on the onset and progression of AIDS in infected individuals.
So much variation is detected at candidate loci at the molecular level that it is often difficult to identify the handful of mutations that are associated with significant phenotypic effects. To solve this problem, we construct an evolutionary tree (clad ogram) of the genetic variation detected at a locus and use this tree to define a nested statistical analysis. The idea is that any phenotypically important mutation is imbedded somewhere in the evolutionary history of the genetic variation at the locus and, therefore, pheotypic effects should be non-randomly distributed over the cladogram. We have shown that this "cladistic" approach is much more powerful than approaches that ignore evolutionary history.
We have extended this cladistic approach to study other evolutionary factors. For example, all genetic variation within a species is influenced by population structure-- system of mating, breeding sizes, and patterns of dispersal. We can therefore use a nested cladistic analysis to study population structure. Moreover, such analyses can separate the effects of current population structure from past events that occurred in the history of the species, such as fragmentation events and geographical range c hanges. These cladistic analyses also provide a rigorous manner to identify species (populations of organisms that behave as distinct evolutionary and ecological lineages).
Finally, we apply these genetic and evolutionary techniques to problems arising in conservation biology. Our laboratory is involved in a variety of conservation biology. Our laboratory is involved in a variety of conservation projects at the local, nati
onal, and international levels.