Chung-I Wu, Ph.D., Chair of the Department of Ecology and Evolution, has taken on the process of evolution at its genetic core. His work, primarily using Drosophila melanogaster, seeks to understand how certain genetic alterations manifest themselves physically to the point where one homogenous population is divided into two different races, and eventually, into two different species.

"My interest has always been in the formation of species, and lately I have taken a step down to look at an earlier event, that is, the formation of races," says Wu. "In most cases, the races eventually merge again, but it is not predictable, and when they continue to diverge, that's when we have species formation."

Wu explains that all new species must pass through this early stage of speciation, called racial differentiation. Wu recognized that, in the case of the African race and the Cosmopolitan races in Drosophila, the mating behaviors had changed to the point where African females weren't excited by Cosmopolitan males. In an effort to understand what the genetic basis for this was, what kinds of genes are involved, and how they caused the differences, Wu and his team carried out gene-swapping experiments. In the case of the African and Cosmopolitan races, the genetic change was manifested in two important ways.


"We took a gene that we hypothesized was a contributor to the racial character differences, in this case desaturase 2, and swapped it between the two species," Wu says.

Wu and his team discovered that while the alteration of this gene did indeed cause the differences in mating behavior, the primary purpose
behind the change was something else.

"What we realized through our gene-swapping experiment was that the primary purpose of this gene was cold tolerance," Wu explains. "When the flies moved out of Africa they had to become more cold tolerant, and that changed their lipid metabolism. But the lipid metabolism change also changed the pheromone of the flies. So the change in this gene has two different manifestations."

Wu's work encompasses not only the resulting physical manifestation of genetic alteration, but also the underlying cause behind such changes, or natural selection.

"We've done a lot of studies on how natural selection affects the genes, how many differences there are among individuals of the same population and of different populations, and how many differences there are among different species," says Wu. "Among species there are many differences, but those differences tend to concentrate among the reproductive systems, specifically male reproductive systems. The most noticeable differences between species, therefore, are how the male reproductive system is constructed. So we see that the incompatibility of male reproductive systems is actually one of the first signs of speciation. The thrust, therefore, is to try to understand how species are different and then to see how natural selection pushes for the difference."

Wu observes that after starting with a more or less homogenous population, something happens where one group changes in a certain way and becomes different from the original population. When one factors into account climate and the changes it brings to the population, you see genetic alterations. "But then there's always this continuous sort of process of selection for mates," Wu adds. "Even when the environment doesn't change at all, changes still occur through the struggle to find the best mate. Males that find a way to excite the females more readily stimulate evolution because then the offspring would have the advantage, be it a call, plumage coloration, the way the male delivers sperm. Therefore the environment does not always drive the biology, but rather sometimes biology simply drives itself."

Wu's work on speciation has been widely recognized by the scientific community, and he has published extensively on his findings, including two recent papers in Science (Vol. 302, November 7, 2003 and December 5, 2003) and one in Nature (Vol. 5, February 2004). His efforts were also recognized by his election to Academia Sinica, the Republic of China's most prominent academic institution.

DISCOVERIES
The BSD to announce the appointment of T. Conrad Gilliam, Ph.D., as Professor and Chairman of the Department of Human Genetics, effective September 1, 2004...

DEVELOPMENT
The new academic year is off to an energetic start. Spark Discovery, Illuminate Life has a new website, which was launched on October 18...

Dollars and Sense
The BSD financial highlights for fiscal year 2004

In Memoriam
Stanley Yachnin, M.D., professor emeritus and former section chief of hematology and oncology at the University of Chicago, died at his daughter's home in Hyde Park on Monday, Aug. 30...

ACCOLADES
Recent Awards and Grants Information for Biological Sciences Division Faculty

ACADEMIC AFFAIRS
Recent Recruitemnts and Appointments of Biological Sciences Division Faculty

More News & Events

Biological Sciences Division
The University of Chicago 5741 S. Maryland Ave, Chicago, IL 60637
773 702 2900    contact@bsd.uchicago.edu