Center for Ecology and Evolutionary Biology
University of Oregon
The genetic basis of parallel evolution in threespine stickleback
February 8, 2008
Engineering Building 110, 4:00 PM
A fundamental problem in evolutionary biology is understanding the developmental genetic basis of evolving traits in natural populations. Over most of the 150 years since Darwin outlined the fundamentals of evolution by natural selection, biologists have had little data on how many genes contribute to evolving traits, what the distribution of allelic effects are across genes, and precisely how alleles interact to generate evolving phenotypes. Due in large part to the recent re-synthesis of evolution and developmental studies (evodevo), a number of these questions are now beginning to be answered. Our laboratory has been contributing to this field by developing the threespine stickleback into a model for evodevo studies. I will describe our progress in understanding the genetic and developmental basis of bony armor loss in Alaskan stickleback, as well as our more recent work on understanding the evolution of head and jaw (craniofacial) morphology. I will also briefly describe our developmental and genomic advances that make the functional dissection of evolving stickleback characters possible. The long term goal of our research is to discover how alleles of genes segregating in natural populations affect cell behaviors and tissue organization, and then use this functional knowledge to better understand the generation and evolution of ecologically relevant phenotypes in the wild. We have just started this journey with stickleback, but our initial findings are already providing surprising insights into age-old evolutionary questions.
A defining feature of life is genetic and phenotypic complexity, which must arise through the accretion of information in the genomes of lineages. But how does this accretion occur, and how is this process related to the generation of phenotypic diversity? Recent work on gene and genome duplication, as well as discoveries in the logic of genetic regulation, are starting to shed light on these questions. Our lab has been tackling this problem on two fronts. First we are exploring the fate of duplicate genes in the stickleback lineage in comparison and other ray fin fish lineages. Teleosts share a whole genome duplication that occurred in a common ancestor at the base of the radiation, and they are also the most diverse group of vertebrates both in terms of numbers of species and amount of phenotypic diversity. Are these related, and if so how? I will discuss our findings and (tentative) conclusions. In addition to our empirical work, we are taking theoretical modeling approaches to understand the origin, accretion and dissemination of genetic modularity. I will present our most recent findings, and discuss how our work, in conjunction with research in many other laboratories, is beginning to address thorny problems in evolution such as the origins of organismal complexity.
Bill Cresko grew up in Tunkhannock, PA, just south of Binghamton. Bill became enamored with aquatic systems during high school field trips to wetlands along the Atlantic coast, and decided to attend the University of Pennsylvania where he majored in biology with an emphasis on ecology. His undergrad research was on the population dynamics of diamondback terrapins in the Chesapeake Bay, and led to his first publication in the journal Conservation Biology. At the same time, Bill took several excellent evolutionary courses, including two taught by Neil Shubin, that were evodevo oriented when the field was just developing. He was hooked, and decided to study evodevo problems using an aquatic system during graduate school. Bill found the work of Dr. Susan Foster on geographic variation in threespine stickleback in Alaska, and knew that with this rapidly evolving fish, living in both marine and freshwater habitats, that he had found an ideal system. Bill joined Susan’s laboratory at Clark University and established a project examining the population and quantitative genetics of divergence along a benthic-limnetic phenotypic axis, and this work was supported by a fellowship from the EPA. Bill then decided to learn much more about the developmental genetic basis of evolving traits, and began postdoctoral work in two zebrafish laboratories at the University of Oregon that was funded by an NIH fellowship. John Postlethwait and Chuck Kimmel both enthusiastically encouraged him to pursue evodevo work on his Alaskan stickleback system. Bill made good immediate progress, with surprising discoveries about the genetic basis of parallel loss of stickleback armor. Bill decided that Oregon was an ideal place to continue his research, and he opened his own laboratory in the Center for Ecology and Evolutionary Biology (CEEB) in the fall of 2005. During his tenure in Oregon, has been fortunate to have his work supported by grants from NSF and NIH. Bill’s little growing family of stickleback researchers are having great fun developing the stickleback system, and his lab has also branched out into exciting new areas such as understanding how the genomes of pipefish and seahorses, close relatives of stickleback, have been modified to form very different morphologies.