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Looks Can Be Deceiving

by Susan Lumpkin

The five species in the family, which they named the
Mohoidae, went extinct between about 1850 and 1980.
The five species in the family, which they named the Mohoidae, went extinct between about 1850 and 1980. (John Anderton

National Zoo geneticist Rob Fleischer acts like an excited kid when he describes some of the fascinating discoveries of his research. In the past year, he came upon “one of the coolest things I’ve ever found!” Fleischer and his ornithologist colleagues Storrs Olson and Helen James, curators in the Smithsonian’s National Museum of Natural History’s Division of Birds, describe the results of DNA analysis of some old museum specimens. The analysis led to some surprising findings: Five species of recently extinct songbirds from the Hawaiian Islands represent a new avian family that no one suspected existed. The five species in the family, which they named the Mohoidae, went extinct between about 1850 and 1980. Previously, there was universal consensus that these nectar-feeding birds were Hawaiian forms of the mostly Australasian honeyeater family, the Meliphagidae. On the face of it, there was no reason to doubt this classification. The only real question, the one Fleischer and his colleagues initially sought to answer, was whether these five species descended from one or multiple immigrant ancestor honeyeater species to the Hawaiian Islands.

These birds look like honeyeaters, right down to their having remarkably similar long, curved bills, fleshy covers over their nasal openings to keep them from snorting pollen, and long, forked, brush-tipped tongues for sucking nectar. They seemed to behave like honeyeaters, and even their loud melodious songs were similar.

But it turned out this is an amazing example of “convergent evolution”—where species evolve to resemble one another, not because they are related, but because of their adaptations to similar ecological opportunities. Fleischer, James, and Olson call this similarity between the extinct Hawaiian birds and the honeyeaters “one of the most deceptive cases of convergent evolution in birds.”

In fact, the mohoids aren’t even kissing cousins of the Australasian honeyeaters. Surprisingly, the Hawaiian birds are most closely related to songbirds that look and behave nothing like them—the fruit- and insect-eating waxwings of North America and Eurasia, New World silky flycatchers, and the palm chat of Hispaniola, which themselves form three distinct families of birds. The researchers’ data suggest that the divergence of the nectar-feeding Mohoidae from their fruit- and insect-eating relatives coincided with the arrival in Hawaii of bird-pollinated flowering plants 14 to 17 million years ago. According to Fleischer, this timing makes the mohoids the oldest known birds to colonize the Hawaiian Islands.

 

More: "The Tales Genes Tell"

More: "A Simple Sequence"

 

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Smithsonian Zoogoer 38(5) 2009. Copyright 2009 Friends of the National Zoo. All rights reserved.