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From: mrh@cybvax0.UUCP (Mike Huybensz)
Newsgroups: net.sci
Subject: Re: Extinctions
Message-ID: <1177@cybvax0.UUCP>
Date: Sun, 5-Oct-86 02:16:57 EDT
Article-I.D.: cybvax0.1177
Posted: Sun Oct  5 02:16:57 1986
Date-Received: Wed, 8-Oct-86 22:00:50 EDT
References: <2357@milano.UUCP> <566@gargoyle.UUCP> <1056@sunybcs.UUCP>
Reply-To: mrh@cybvax0.UUCP (Mike Huybensz)
Organization: Cybermation, Inc., Cambridge, MA
Lines: 30

In article <1056@sunybcs.UUCP> Col. G. L. Sicherman writes:
> It's sometimes a matter of taste whether to classify two organisms as
> different species or just different varieties of the same species.
> With livestock or trees it's easy to decide; not always so with
> bacteria or viruses.  In the course of evolution, species sometimes
> merge or split; then how do we keep score?

Actually, it's not easy to decide even for well known animals and plants.
As you might expect, there is a continuum of degrees of variation between
populations, and as time passes, our tools for discerning the smaller
but significant variations improve.

For example, the common leopard frog of the eastern US was thought to be
one species until about 10 years ago when it was discovered to be at least
four, each with distinctive mating songs that provided reproductive
isolation.

The exact score isn't too important: the idea is to measure the genetic
diversity by assuming that number of species is roughly representative of
genetic diversity.  However, the species numbers of smaller organisms are
badly under represented because we can't yet effectively distinguish them from
eachother.  These cryptic species are a major taxonomic problem.  In my own
field, the mites, there are groups which are well known to be chaotic: because
the animals all look extremely similar, but won't interbreed.  Eventually we
may be able to look directly at their genetic diversity and finally resolve
these questions, but in the mean time we are probably dreadfully
underestimating just how much diversity is out there in very small packages.
-- 

Mike Huybensz		...decvax!genrad!mit-eddie!cybvax0!mrh