LAUSR

The genetic and molecular mechanisms that underlie the amazing diversity of living species have been uncertain and contentious. We have been using stickleback fish as a model system to reveal how new traits evolve in natural populations. These fish have undergone widespread and repeated evolution in postglacial lakes and streams in the Northern Hemisphere. Dramatically different morphological forms can still be crossed, making it possible to genetically map the specific genes and DNA changes that underlie recurrent adaptation to new environments. Our studies show that new traits can evolve in natural populations through changes in the expression of key developmental control genes. Although the same control genes are essential for normal viability, regulatory changes make it possible for natural fish populations to evolve dramatic new phenotypes while preserving overall fitness. Strikingly, the same genes andmechanisms are used repeatedly when key differences evolve in many different lineages. With the advent of large-scale DNA comparative sequencing and genome editing methods, it is now becoming possible to extend these results more generally, providing new insights into evolution of many different organisms, including ourselves.