Assistant Professor of Biology, Molecular Biology Program, University of Utah, Salt Lake City, UT 84112
What are the genetic and developmental origins of unique traits in natural populations and species of vertebrates? Both evolutionary and medical biologists are interested in the ways that genotypic changes can influence growth and morphology, yet we know remarkably little about the genetic and developmental mechanisms that generate natural morphological diversity. For example, in most cases of adaptive skeletal evolution, we do not know how many genes are involved, which genes are actually responsible for morphological change, whether alterations to these genes affect coding or regulatory regions, or whether the same genes are involved repeatedly in the evolution of similar traits in different populations and species. To address these topics, we combine genetics, developmental biology, and fieldwork to study morphological evolution in both natural and domesticated populations of vertebrates.
Genetic architecture of evolutionary change. Sticklebacks are ideal model organisms for genetic and developmental studies of natural populations because different populations of these fish vary dramatically in skeletal structures, yet fish from throughout the Northern Hemisphere can be readily crossed in the laboratory for genetic mapping experiments. Previous work determined that cis-acting regulatory changes in the Pitx1 locus are responsible for hind fin (pelvis) loss in a population of threespine sticklebacks (Shapiro et al., 2004, Nature). More recently, we showed that both similar and different genetic changes control pelvic reduction in ninespine sticklebacks (Shapiro et al. 2006, PNAS; Shapiro et al., 2009, Current Biology), a different genus of fish that last shared a common ancestor with threespine sticklebacks over 10 million years ago. By comparing the genetic basis of other traits between the two different types of fish, we can critically test whether similar genetic mechanisms repeatedly underlie similar adaptive phenotypes, a topic of enduring interest to geneticists and evolutionary biologists.
Darwin’s pigeons. In The Origin of Species, Charles Darwin enthusiastically promotes the enormous diversity among domesticated pigeons – generated by thousands of years of artificial selection on a single species by human breeders – as an important proxy for understanding natural selection in wild populations and species. Indeed, he notes that the vast diversity among pigeon breeds within a single species is reminiscent of levels of diversity among multiple genera of other birds. What is the genetic basis of this tremendous variation? Pigeons offer a promising opportunity to study many ecologically and evolutionarily relevant traits that vary among birds. We are generating novel genetic tools for the pigeon to map the number and location of genes that control important characteristics such as craniofacial morphology, pigmentation, feather outgrowth, and behavior. This work will serve as an important entry point to dissecting the genetic basis of the astounding variation in wild avian species.
Broader implications. Many aspects of development are highly conserved among vertebrates. Thus, new insights gleaned from our work will illuminate the genetic mechanisms that control tissue growth, morphology, and functional traits in many other organisms. Ultimately, our studies of variation generated by natural and artificial selection will inform our understanding of the genetic basis of adaptive evolutionary change.