for National Geographic News
With winter cold settled over much of North America, it would be hard to
blame any native of Canada for contemplating a move to Hawaii. So
perhaps it should be no surprise that Canada geese did it some time
ago.
Unexpectedly, scientists have learned that the
distinctive-looking and endangered Hawaiian goose, known as the nene
(nay-nay), is a not-so-distant relative of commonly known Canada geese.
"Rather than being a sister species of the Canada goose, the nene is an
evolutionary descendent of the Canada goose," said Helen F. James, a
biologist at the Smithsonian Institution in Washington, D.C.
The discovery shows how quickly a population that becomes isolated can develop specialized adaptations, especially when its new habitat happens to be a young island with few animals already in residence.
Sadly, the story of the nene's closest relatives—two extinct species of Hawaiian geese—also indicates how rapidly isolated populations can be exterminated by human activities.
The finding suggests the need for a re-classification of living Canada geese by subdividing them into two separate groups: those closely related to the nene and those more evolutionarily distant.
Based on genetic similarities, the second group would also include the barnacle goose, a population of distinctive-looking geese that is currently recognized as a species by itself.
Considered Hawaii's state bird, the nene lives in a considerably different environment than that of its Canadian kin. "We are used to seeing Canada geese in wetlands and near water," said James. But in their adopted tropical habitat of Hawaii, the birds "evolved to become more independent of wetland habitats," she said.
The Hawaiian goose also sports distinctive plumage. "Canada geese have all black necks, whereas nene have the sides and front of the neck buff-colored with distinctive dark furrows," said James.
These outward differences belie a strong genetic resemblance and a close evolutionary link between the birds. In fact, the nene is more closely related to some subspecies of Canada geese than some of the Canadian subspecies are to each other, according to research conducted by James, Ellen E. Paxinos, and their colleagues.
The surprising discovery will help scientists understand how—and how quickly—Hawaii's birds evolved to become different from their ancestors that first settled the Pacific islands.
Goose Chase
The researchers' finding suggests that the nene and several other species of Hawaiian geese now extinct branched off from a population of Canada geese and colonized the tropical paradise about half a million years ago.
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