Real species and ideology

[Michael Bayly]

Hi Richard,

A key part in differentiating the two patterns (morphocline vs. introgressive hybridization) can be an understanding of the broader relationships of the taxa involved.  You omitted the last, perhaps most critical, part of Curtis' statement on the mater. As he said:
 "(It especially helps if the two intergrading species turn out not to be sister
species!)"

Populations that form part of a differentiating morphocline would be monphyletic or possibly paraphylethic - and this could be demonstrable with genetic data.

On the other hand, introgressing taxa (previously distinct species that have come together and started to hybridise) need not be each others closest relatives - and this could also be demonstrable with genetic data (and suitable markers could then be used to investigate the extent of introgression).

If the two "messy" (clinal or introgressing) taxa are most closely related (or even paraphyletic with respect to some peripheral isolate(s)) the problem is obviously a lot more complicated.  Either process could/would produce a similar pattern of variation (morphological or genetic), and the conundrum you are talking about still raises its head......

Mike

----------------
Michael Bayly
Research Scientist in Plant Biosystematics
Museum of New Zealand Te Papa Tongarewa
PO Box 467 
Wellington, New Zealand
Ph: +644 381 7262
Fax: +644 381 7070



-----Original Message-----
From: Taxacom Discussion List [mailto:TAXACOM at LISTSERV.NHM.KU.EDU]On
Behalf Of Richard Pyle
Sent: Wednesday, 21 April 2004 6:45 a.m.
To: TAXACOM at LISTSERV.NHM.KU.EDU
Subject: Re: Real species and ideology


> It is often a non-trivial task to distinguish between two
> subspecies separated by a morphocline, on the one hand, and two species
> separated by an area of introgressive hybridization, on the other, but
> genetic tools can often be brought to bear to sort out these issues.

How would you distinguish the two separate patterns (morphocline of
subspecies vs. introgressive hybridization) -- even with the best of genetic
tools?  Indeed, is there anything fundamentally different between the two
patterns, other than our artificial imposition of the rank "species" in one
case, and "subspecies" in another?

This gets right to the heart of my original question to you, about defining
the terms "real" and "artificial" in an evolution/species context, and in
supporting one perspective over the other.  This thread has taken a
different direction than what I had hoped it would, but the above quote from
Curtis brings it back to what I'm most interested in understanding.

Aloha,
Rich

=======================================================
Richard L. Pyle, PhD
Ichthyology, Bishop Museum
1525 Bernice St., Honolulu, HI 96817
Ph: (808)848-4115, Fax: (808)847-8252
email: deepreef at bishopmuseum.org
http://www.bishopmuseum.org/bishop/HBS/pylerichard.html
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