Evolution may sometimes happen so fast that it's hard to catch in action, a new study of Galápagos finches suggests.
Researchers from New Jersey's Princeton University have observed a species of finch in Ecuador's Galápagos Islands that evolved to have a smaller beak within a mere two decades.
Surprisingly, most of the shift happened within just one generation, the scientists say.
In 1982 the large ground finch arrived on the tiny Galápagos island of Daphne, just east of the island of San Salvador (map of the Galápagos).
Since then the medium ground finch, a long-time Daphne resident, has evolved to have a smaller beak—apparently as a result of direct competition with the larger bird for food.
Evolutionary theory had previously suggested that competition between two similar species can drive the animals to evolve in different directions.
But until now the effect had never been observed in action in the wild.
In the new study Princeton's Peter and Rosemary Grant closely tracked the two related species for decades.
Their results appear in this week's issue of the journal Science.
Changing Beaks, Changing Diet
For both finch species, the researchers note, feeding is a trade-off between effort and payoff.
The birds generally prefer to eat larger seeds, which are harder for their nutcracker-like beaks to break open but hold a bigger reward inside.
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