The researchers found strong evidence that the EphB2 (Ephrin receptor B2) gene acts as an on-off switch to create a head crest when mutant, and no head crest when normal.
They also showed that the mutation and related changes in nearby DNA are shared by all crested pigeons, so the trait evolved just once and was spread to numerous pigeon breeds by breeders.
Full or partial genetic sequences were analyzed for 69 crested birds from 22 breeds, and 95 uncrested birds from 57 breeds. The biologists found a perfect association between the mutant gene and the presence of head crests.
They also showed that while the head crest trait becomes apparent in juvenile pigeons, the mutant gene affects pigeon embryos by reversing the direction of feather buds--from which feathers later grow--at a molecular level.
Other genetic factors determine what kind of head crest each pigeon develops: shell, peak, mane or hood.
Tracking the origins of pigeons
A 2012 study by Shapiro provided limited evidence of pigeons' origins in the Middle East and some breeds' origins in India and indicated kinship between common feral or free-living, city pigeons and escaped racing pigeons.
In the new study, "we included some different breeds that we didn't include in the last analysis," Shapiro says. "Some of those breeds only left the Middle East in the last few decades. They've probably been there for hundreds if not thousands of years. If we find that other breeds are closely related to them, then we can infer those other breeds probably also came from the Middle East."
The scientists found that the owl breeds--pigeon breeds with very short beaks that are popular with breeders--likely came from the Middle East. They're closely related to breeds from Syria, Lebanon and Egypt.
The research also uncovered a shared genetic heritage between breeds from Iran and breeds likely from India, consi
|Contact: Cheryl Dybas|
National Science Foundation