Explore a comprehensive lecture on the role of large-effect loci in adaptation, focusing on introduced stickleback populations. Delve into Fisher's model, phenotypic adaptation following freshwater colonization, and the genetic basis of armor differences. Examine how gene discovery is transforming adaptation studies, with emphasis on multiple genes differentiating marine from freshwater populations. Analyze experimental data from F2 and F3 generations, including fitness mapping to the Eda region and its impact on lateral plate morphology. Investigate the two-fold fitness difference between genotypes and changes in allele frequency over time. Compare findings with a second introduced population across multiple generations, and critically evaluate the contribution of large-effect loci to adaptation in nature.