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From: g-rh@cca.UUCP
Newsgroups: talk.origins,sci.bio
Subject: Re: question about animal hybridization
Message-ID: <14184@cca.CCA.COM>
Date: Sat, 21-Mar-87 09:11:12 EST
Article-I.D.: cca.14184
Posted: Sat Mar 21 09:11:12 1987
Date-Received: Sun, 22-Mar-87 21:33:33 EST
References: <3353@ihlpa.ATT.COM]
Reply-To: g-rh@CCA.UUCP (Richard Harter)
Organization: Computer Corp. of America, Cambridge, MA
Lines: 31
Keywords: evolution speciation clines
Xref: utgpu talk.origins:440 sci.bio:159
Summary: Clines are the answer

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 know this is not the definition
] of species !)
] 
] 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! )
] 
	You are talking about clines (a chain of sub species).  a specific
example is the herring gull cline consisting of

(1) The British lesser black-backed gull, Larus fuscus graellsii,
(2) Scandanavian lesser black=backed gull, Larus fuscus fuscu,
(3) Siberian vega gull, Larus argentatus vegae,
(4) American herring gull, Larus argentatus smithsonianus,
(5) British herring gull, Larus argentatus argentatus

1 can interbreed with 2, 2 with 3, and so on, but 5 and 1 cannot
interbreed.  The difference is one of size -- the British herring
gull is twice as big as the lesser black-backed gull.

-- 

Richard Harter, SMDS Inc. [Disclaimers not permitted by company policy.]