BOB HIRSHON (host):
A species’ geographic divide. I’m Bob Hirshon and this is Science Update.
The common yellowthroat is a songbird found throughout most of North America. They’re mostly brown in color, but males of the species have bright yellow breasts and prominent black facial masks. Females find these markings attractive and choose their mates based on them. But when researchers working in two different states let the females choose which ornament they liked best, they were surprised. Peter Dunn is a biologist at the University of Wisconsin, Milwaukee.
PETER DUNN (University of Wisconsin at Milwaukee):
What we found is that the females in New York preferred males with larger yellow breasts and females in Wisconsin preferred males with larger black facial masks.
Female sexual selection like this is a major cause of variation in species and even a factor in the evolution of new species. I’m Bob Hirshon, for AAAS, the science society.