The white-throated sparrow is considered a good model organism for the genetic basis of behavior due to a genetic event that has divided the species into two distinct forms that differ in their behavior. These two forms, the white-striped morph and the tan-striped morph, are easily distinguished by their plumage markings.
At some point during the evolution of the species, a chromosome broke and flipped. This process, called an inversion, rearranged the sequence of the chromosome.
The white-striped birds, which all possess at least one copy of the rearranged chromosome, tend to be more aggressive and less parental than the tan-striped birds, which do not have the rearranged chromosome.
"The two morphs work beautifully in evolution because one color morph almost always mates with the opposite color morph," Horton says. "They complement each other."
For the past decade, the Maney lab has been a leader in documenting the neuroendocrine and genetic differences between the white-throated sparrow morphs. For the current study, funded by the National Institutes of Health, Maney recruited Horton, a field biologist and an expert in the natural history of the white-throated sparrow.
"At heart, I'm a behavioral ecologist," Horton says. "I want to integrate neuroscience and genetics into my work to understand the behaviors that I see in the wild."
The scientists knew that the different behaviors of the two sparrow morphs were linked to the chromosome inversion. "We wanted to know what genes captured by that chromosome also differ between the morphs, in order to identify the genetic mechanisms that may explain the behavioral differences," Horton says.
The white-throated sparrow winters in the South, but mates and raises its young during spring and summer in the North. "In a sense, I migrated with these birds," Horton says, explaining how he conducted fieldwork over three years. Each summer, he pack
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Emory Health Sciences