XVI International Botanical Congess

Epistasis (gene interaction) is a fundamental assumption of many evolutionary models. However, little is known of its role in the evolution of natural populations. We quantified the contribution of epistasis to population differentiation in the annual, outcrossing legume, C. fasciculata. Based on hybrid performance in the field we found that epistasis among linked genes contributed substantially to population differentiation. These results were confirmed in a common garden experiment where epistasis sometimes contributes to trait divergence. We also observed that nuclear x cytoplasmic interactions were found to have significant effects on fitness, with matches between cytoplasm and nuclear genes conferring the highest fitness. We discuss our results in terms of what they reveal about the evolutionary process.