Researchers from the Texas A&M College of Veterinary Medicine and Biomedical Sciences have identified that the white-tipped feathers found in many chicken breeds arise from multiple independent mutations rather than a single genetic source. The study, published in Animal Genetics, details how at least three distinct mutations involving the same pigmentation gene can produce mottling, a pattern characterized by white feather tips.
Dr. Leif Andersson, a professor in the VMBS Department of Veterinary Integrative Biosciences, noted that mottling is unusual because these different mutations result in a very similar phenotype. Typically, a physical trait shared across multiple breeds traces back to one specific mutation that spread through breeding. However, mottling followed a different evolutionary path.
The mutations arose independently in different groups of chickens and were preserved through selective breeding.
The pattern occurs when pigment cells do not migrate normally as feathers grow. If these cells do not reach the end of a developing feather, the tip remains white. On chickens with otherwise black feathers, this creates a spotted appearance across the plumage.
Andersson explained that humans bred chickens carrying these different mutations because they preferred the feather pattern, and the mutations had no negative effect on egg or meat production.
This process represents parallel evolution, where similar traits develop separately in different populations. The findings demonstrate how selective breeding can preserve genetic diversity that might otherwise remain rare. Andersson stated that humans appreciate diversity among domestic animals as long as a mutation does not cause harm to the animal.
