Adaptation is widespread in nature. Despite its obvious importance, we know little about how adaptation evolves. Dr. Chan will start by describing what we have learnt from classical genetic mapping that connect single adaptive mutations to phenotypic variation and population divergence. Then discuss the application of a new approach, Parallel Selection Mapping, to uncover the genetic basis of a polygenic trait in artificially selected laboratory mice and naturally selected wild mice.

Bodyweight is a classical complex trait controlled by many genes that has been difficult to dissect genetically. It affects fitness and shows parallel increases in island populations of rodents (island gigantism). In a number of independent mouse experiments starting in the 1970s, it has been subjected to long-term artificial selection. By applying parallel selection mapping to these artificial selection lines, Dr. Chan will demonstrate how we can tackle the bodyweight complex trait, and break it down into its individual genetic components. In doing so, he will show how we can systematically identify loci controlling parallel adaptation via re-use of standing genetic variation.

Dr. Chan will discuss several general principles emerging from the genome-wide pattern, including the importance of pre-existing genetic variation to adaptation; the clustered genetic architecture and nature of a multilocus response to selection; and the connection between loci under artificial and natural selection, such as island gigantism. He will end by discussing some of the emerging results from the first genome-wide molecular study of the wild populations of gigantic Faroese mice, and our current effort in investigating how they have evolved to be among of the largest wild mice in the world.