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From: howard@cpocd2.UUCP
Newsgroups: talk.origins,sci.bio
Subject: Re: question about animal hybridization
Message-ID: <522@cpocd2.UUCP>
Date: Tue, 24-Mar-87 12:21:59 EST
Article-I.D.: cpocd2.522
Posted: Tue Mar 24 12:21:59 1987
Date-Received: Fri, 27-Mar-87 00:48:07 EST
References: <3353@ihlpa.ATT.COM>
Reply-To: howard@cpocd2.UUCP (Howard A. Landman)
Organization: Intel Corp. ASIC Services Organization, Chandler AZ
Lines: 27
Xref: utgpu talk.origins:457 sci.bio:166

In article <3353@ihlpa.ATT.COM> lew@ihlpa.ATT.COM (Lew Mammel, Jr.) writes:
>In a discussion about possible mechanisms of speciation, the question
>of genetic compatibility as a criterion for typological classification
>came up.  That is, animals which when cross-bred produced viable, fertile
>offspring might be classified together.
>
>I asserted that this criterion doesn't generate an equivalence relation,
>since there might be populations A, B, and C, such that A is compatible
>( by the above criterion ) with B, B is compatible with C, but A is not
>compatible with C.
>
>My question is, is there an example of this intransitivity among known
>populations of animals? ( N.B. animals, not plants! )

Yes.  The classic example is frogs in the Appalachians.  Northern frogs
can interbreed with their nearest neighbors, who can interbreed with
those a little farther south, ... and so on.  But the northernmost and
southernmost frogs cannot interbreed.  I first heard of this in the late
60's, but I don't have a reference.

Note that there may be gender-dependence as well.  It is possible that
A males could breed with B females, but B males can't breed with A females.
(No I don't have an example.)
-- 

	Howard A. Landman
	...!intelca!mipos3!cpocd2!howard