Sara Fauver, University of Utah
Life Sciences
We know that novel genetic variants have driven evolution for millions of years and that natural selection favors phenotypes most suited for survival, leading to the enormous diversity of life we see today. However, what remains unclear, are the patterns of mutations that lead to large phenotypic changes. For example, do mutations in a single gene of large effect lead to morphological changes more often than numerous mutations in genes of smaller effect? Also, do these mutations occur more often in protein coding regions or regulatory regions of DNA? Finally, are the same genes or gene pathways used repeatedly across lineages when parallel phenotypes evolve?
These questions have led geneticists to study stickleback fish, a group of species that is remarkable because of its relatively recent evolutionary history. Approximately 10,000 years ago, at the end of the last ice age, freshwater lakes formed throughout the Northern Hemisphere as glaciers retreated northward. Marine stickleback, which had previously been confined to habitats at the glacial perimeters, began to colonize these newly available habitats, and these new populations faced similar selective pressures in freshwater (for example, novel prey sources and physiological constraints associated with freshwater). New predators, specifically grasping insect larvae, may also have contributed to the predictable morphological changes associated with a shift to freshwater, including loss or reduction of the pelvic skeleton.
One ninespine stickleback population in particular, the Salt River (freshwater) population, includes fish that show a wide range of pelvic phenotypes. This suggests a complex genetic mechanism for pelvic reduction is responsible for evolution in the Salt River. Our current research is directed at identifying and understanding the mechanisms at play in this population and how they compare to other stickleback populations. This knowledge will help us add another piece to the evolutionary morphology puzzle.