Birds of a Feather

BU Today

Tucked away in an unassuming gray metal file cabinet in a graduate student office at Boston University is an evolutionary puzzle that would leave even Charles Darwin scratching his head. Inside the cabinet, 18 clear Tupperware containers house 301 estrildid finch specimens from New Guinea, carefully laid out in rows by population and species. Each of the 11 species’ plumage is splashed with its own distinct pattern of black, brown, gray, and white.
Michael Sorenson, a professor of biology, explains that the birds are an evolutionary anomaly: despite their striking coloration differences, all 11 species are extremely closely related, suggesting that they evolved quickly and recently (evolutionarily speaking), even faster than the famous Darwin’s finches of the Galapagos.
But how and why did these close relatives end up looking so different? And how did they evolve so quickly and rapidly into different species? Biologists have long wondered exactly how new species form, but generally assume that new genetic mutations account for the changes in form and function that ultimately make each species unique. However, that may not always be the case, and studying unusual groups like the finches of New Guinea helps biologists better understand other ways new species emerge, revealing more about evolution as a whole.
“Speciation is the process by which the incredible diversity of life on Earth came into being—including humans,” Sorenson says. “It is not only one of the most fundamental processes in evolutionary biology, but is central to understanding the history of life on Earth.”
To understand how this extraordinary group of finches evolved, Katie Stryjewski (GRS’15) collected birds throughout New Guinea and carefully preserved blood, feather, and tissue samples, with Sorenson joining her on the last of four trips. Then Stryjewski used genome sequencing to peer deep inside the birds’ genetic codes.
Photo by Cydney Scott
Sorenson first became interested in the estrildid finches of New …

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