http://www.newscientist.com/news/news.jsp?id=ns99996762
Birds of a feather not related to each other
09:30 11 December 04
If it walks like a flamingo and looks like a flamingo, it is not
necessarily a flamingo - or even a close relative. A controversial
genetic study suggests we have completely misunderstood how the
majority of birds are related, and that some species that look almost
identical are not related at all.
The discovery comes from an analysis of the evolution of the bird gene
beta-fibrinogen . It suggests that the Neoaves, a group that includes
all modern bird species except waterfowl, landfowl and flightless
birds, actually comprises two distinct lineages called the Metaves and
Coronaves, and that many birds which look alike are not in the same
lineage.
For instance, flamingos and roseate spoonbills - two pink, long-legged
wading birds with similar-looking heads, wing shapes and plumage - are
not related as previously thought. Flamingos, it turns out, belong to
the Metaves, while spoonbills belong to the Coronaves.
Matthew Fain and Peter Houde at New Mexico State University in Las
Cruces, US, analysed the number of different nucleotides found on
beta-fibrinogen across some 150 bird families. From that the
researchers constructed a new avian evolutionary tree.
Convergent evolution
They found two major lineages, each of which contains many examples of
convergent evolution, the process by which two species that do not
share a recent evolutionary history nevertheless end up looking alike
and inhabiting a similar ecological niche.
Both lineages contain owl-like nocturnal predators, birds with long
curvy beaks that live on nectar, broad-winged oceanic divers and birds
that evolved splayed toes to help them live in trees. Using this
classification, boobies and tropicbirds, two similar-looking types of
seabird, now belong to Coronaves and Metaves, respectively.
“People have been trying to classify birds based on their appearance
for hundreds of years. It is valuable at some levels, but when you get
to really deep divergences, you just hit a wall,” Houde says.
But Joel Cracraft at the American Museum of Natural History in New
York, US, is not convinced. “The base of modern birds is a very
difficult problem to resolve. This is a welcome data set, but it’s not
going to be this simple,” he says. Fain and Houde are working with 11
other genes to corroborate their results.
Journal reference: Evolution (vol 58, p 2558)
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