The findings are the first report of such quick evolution in a mammal and appear in the May 22 issue of the journal Nature.
Oliver Pergams, a conservation biology researcher with the Chicago Zoological Society in Brookfield, Ill. and visiting research assistant professor at UIC, conducted the research as his Ph.D. thesis project at UIC with Dennis Nyberg, associate professor of biology.
Pergams' study began as a comparison of the genetics of two mice common to the Chicago region -- the white-footed mouse and the prairie deer mouse. But the search for historical samples quickly showed the white-footed mouse had squeezed out the prairie deer mouse from its dominant position, diminishing the samples needed to do a comparative study, so Pergams and Nyberg focused attention on the white-footed mouse.
"This intensified focus resulted in our discovery of rapid evolution," said Pergams. "It was a great surprise. We were simply trying to quantify the amount of genetic variation over time, not show evolution."
The researchers analyzed DNA samples taken from 56 museum specimens dating as far back as 1855, along with 52 recently captured mice from local forest preserves and state parks. Wayne Barnes, professor of biochemistry and molecular biophysics at the Washington University in St. Louis School of Medicine, assisted in analyzing the DNA.
The changes in gene sequence frequencies were dramatic, Pergams said, across the three 50-year intervals studied.
Only one of the mice from the latest period had the same DNA sequence as the most common sequence among the mice collected before 1950. The first mouse with the sequence currently common was captured back in 1906 at Volo Bog
Contact: Paul Francuch
University of Illinois at Chicago