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A National Science Foundation-funded study found that Charles Darwin's famous finches defy what has long been considered a key to evolutionary success: genetic diversity. The research on finches of the Galapagos Islands could change the way conservation biologists think about a species' potential for extinction in naturally fragmented populations.
Researchers examined 212 tissue samples from museum specimens and living birds. Some of the museum specimens in the study were collected by Darwin himself in 1835. Only one of the extinct populations, a species called the vegetarian finch, had lower genetic diversity compared to modern survivors. Specifically, researchers believe a biological phenomenon called sink-source dynamics is at play in which larger populations of birds from other islands act as a "source" of immigrants to the island population that is naturally shrinking, the "sink." Without these immigrant individuals, the natural population on the island likely would continue to dwindle to local extinction. The immigrants have diverse genetics because they are coming from a variety of healthier islands, giving this struggling "sink" population inflated genetic diversity.Image credit: Jose Barreiro