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From: dean@violet.berkeley.edu (Dean Pentcheff)
Newsgroups: sci.bio
Subject: Re: The Red Queen (really: Eyeless fishes)
Message-ID: <2103@jade.BERKELEY.EDU>
Date: Wed, 7-Jan-87 01:30:48 EST
Article-I.D.: jade.2103
Posted: Wed Jan  7 01:30:48 1987
Date-Received: Wed, 7-Jan-87 18:42:58 EST
References: <741@aecom.UUCP> <927@husc6.UUCP> <124@bcsaic.UUCP>
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Reply-To: dean@violet.berkeley.edu (Dean Pentcheff)
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Organization: University of California, Berkeley   Department of Zoology
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Summary: polyphyletic origin (?) implies advantage?

In article <124@bcsaic.UUCP> michaelm@bcsaic.UUCP (Michael Maxwell) writes:
>I suggested this [genetic drift] in answer to an exam question once, as 
>the origin of blind
>(eyeless) cave fish.  (The incidence of eyeless fish is quite high, but for
>obvious reasons the eyeless ones seldom make it very far in life up here.)
>The professor didn't like my answer...his point was that there had to be a
>selective advantage to blindness in cave life.  I didn't believe so at the
>time, and I'm still skeptical.  Anyone care to comment?

I'm not sure, but I suspect that eyelessness in cave fish arose
independently from several groups of (eye-bearing) fish.  If this is
the case, it seems unlikely that cave fish stemming from different
ancestral groups would share the _same_ trait due to drift, given that
there are only a few characters that tend to be different in cave fish
(lack of eyes, lack of pigment).  If, on the other hand, the trait
conferred a selective advantage, then its appearance in several groups
is reasonable.  The advantage (presumably) has something to do with
energy savings for the eyeless fish (though this is a rampantly
"selectionist" argument).

-Dean	(dean@violet.berkeley.edu)