At 23:51 18/8/97 -0700, Michael Price wrote: (snip)

>I'm quite willing to watch the debate go on as it has for years with all the
>pleasure of an old pooch settling back down to a good bone that he's been
>working on for a good long time already, but is it not possible to do some
>DNA work on this complex and lay this one to rest for aye?

It would be possible to do some DNA work on the complex and it would
be very interesting to see the results. However, it wouldn't necessary end
the debate once and for all.
The problem with using DNA to answer the species question is much
the same as it is for morphology and other methods: how different is
different enough? Geneticists can calculate genetic distances which
measures how far apart the birds are genetically. But there is no agreement
on how much genetic distance two types must have before they are different
species. In general, birds are much more closely related to one another
than mammals are. So the genetic distances between mammal species are equal
to the genetic distances between bird families or orders!
In some cases, genetic data works great. The Long-billed Murrelet
was split from the Marbled Murrelet because genetic data clearly showed that
Marbled Murrelets from North America were more closely related to Kittlitz's
Murrelets than they were to the "Marbled Murrelets" from Asia. The birds in
Asia were given species status and called the Long-billed Murrelet.
However, rarely are the results are so clear cut. Usually, the types are
closely related and we have to decide where to draw the line.
Genetic data can also yield conflicting results. One marker may
show one relationship while another marker shows a different relationship.
As a result, data from many different markers may be necessary before a
clear relationship is revealed. Until the cost of genetic analysis goes
down, it is unlikely that this type of data will be gathered for very many
species.
DNA work is a power tool for looking at these questions but it isn't
the final answer to the species question.
Deb Beutler
Department of Zoology
Washington State Univerisity
Pullman, Whitman Co., WA
dbeutler at wsunix.wsu.edu