Molecular vs morphological avian systematics

Michael Gochfeld gochfeld at eohsi.rutgers.edu
Wed Feb 6 23:58:09 EST 2002


No sooner had I completed my circumlocutious discourse on conservative
taxonomy than the following crossed my virtual desk forwarded by Neal
Smith
=================================================

Neal Smith wrote:

> I sent out the PDF and the text on this one already. Compare it with what THE ECONOMIST has to say. Then you can decided if you will give interviews to this magazine after your next PNAS paper!!!!!!!!!!!!!!!!
>
> I think that they did a rather good job with some pointed comments thrown in....
> No real naturalist would list a mtDNA species (now known as "conservation species" in this politically correct world).............!!!!!!!!!!!!!!!!!!!
>
> Avian evolution A wild goose chase
> Jan 31st 2002 From The Economist print edition
>
> Feathers are flying in the world of bird classification
>
> NATURAL selection follows no plan, which makes human attempts to classify biodiversity inevitably messy. A study on geese just published in the Proceedings of the National Academy of Sciences by Robert Fleischer of the Smithsonian Institution in Washington, DC, and his colleagues, nicely illustrates this messiness. It also illuminates the sometimes arbitrary way that conservationists decide what is worth conserving, and what is not.
>
> Taxonomists, the scientists charged with classifying the living world, have traditionally used anatomy as their principal tool. If it looks like a goose and waddles like a goose and hisses like a goose, then the chances are that it is a goose. And if it looks more like one species of goose than another, it is probably more closely related to the former than the latter. But not inevitably. Looks evolve in response to the environment. Unrelated species in the same environment may end up looking similar. Related species in different environments may end up looking different.
> When an environment is crowded with existing species, the scope for novelty is limited by what is already there. New volcanic islands, though, offer new opportunities for whatever species get there first. And on the newly erupted island of Hawaii, it transpires, one of the early arrivals was a flock of geese.
> The nene (pronounced neh-neh), Hawaii's native goose, is one of conservation's most famous success stories. The species was brought back from the brink (only 30 individuals left in the 1950s) to a point where, while it is still classified as endangered, it seems reasonably safe from the vicissitudes of fortune. Fossil skeletons found in lava tubes on the island, though, show that the nene was not originally alone. At least two other species of goose existed there until people arrived and, presumably, ate them. They would have made easy prey. Both were large. One was completely flightless. And the other had the aerial prowess of a barnyard chicken.
> That makes perfect sense. There were no predators on Hawaii until people arrived. Flight is costly. So, why bother? But the anatomical modifications which show biologists that these extinct species were not the world's greatest aviators, also serve to obscure their origins.
> Dr Fleischer and his team were able to look beyond anatomy by comparing the DNA sequences of some of the birds' genes. And, since they were able to extract useable samples of DNA from some fossils, they were able to do so for both the living and the defunct geese.
> The goose family tree thus revealed held some surprises. That the three sorts of Hawaiian goose were close relatives was the least of them. That these three geese were related to Canada geese was also not that surprising, at least for the nene, which traditional classification had pointed in that direction. What was a surprise was that Canada geese themselves (which are currently divided into 11 subspecies) fall into two disparate groups, and that the Hawaiian geese, hitherto seen as "proper" species, are merely additional subspecies within one of these groups. (To add to the confusion, the barnacle goose, also seen hitherto as a proper species, is actually part of the other Canada-goose group.)
> It seems, therefore, that all of Hawaii's geese, both extinct and living, are descended from Canada geese. Given the isolation of the islands, and the branching of the family tree, the chances are that all descend from a single off-course flock that arrived about 500,000 years ago.
> Dr Fleischer's tree also suggests it may be time to abandon the Canada goose as a distinct species, and elevate its many subspecies one rung up the taxonomic ladder. The logical alternative is that the nene¯that icon of successful conservation¯is merely a subgroup of a species that farmers and park-keepers around the northern hemisphere regard as a pest. And if that were the case, would people be as keen to preserve it as they are now?
>

 
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