species reality (was species/subspecies query)

Thu Nov 16 10:52:09 CST 2000

>>> From: Curtis Clark:
IMO there are only two legitimate positions:
1) Species are not actual units of nature
2) Species are units of nature that originate through a process or processes
that we call speciation<<<

3) Species are units of nature that originate through speciation, but like
so many aspects of nature there is some statistical slop about them.  I've
never heard an official name given to my preferred species definition, and I
call it the "Genetic Species Concept", that a species is an evolutionary
unit.  As such, there is genetic cohesiveness at a given time, but that
*doesn't* mean genetic homogeneity, nor does it mean genetic stasis over
evolutionary time.

While I agree that such ideas as "potential interbreeding" and "incipient
speciation" can be "just so" stories and untestable (at least in practice),
they can also be true sometimes.  [Just because I'm paranoid doesn't mean
they're not out to get me!  Just because I won't be around long enough to
see if speciation goes to completion doesn't mean the process isn't
happening!  Just because I can't account for all individuals in both
populations at all times doesn't mean there hasn't been some movement
between them!]  Gene flow is a continuum from 0 to 100% (panmixia).  At or
near the extremes, it's easy to decide if something is a species or not, but
there's no reason to believe intermediate values don't occur.  We can accept
the concept of species because most situations we look at have gene flow
"near" the extreme values.  There are exceptions, the concept of species is
not perfect, but that doesn't mean it's useless or imaginary.  Biology is
about averages, approximations, and simplifications, and any concept that
works at that level can be a useful one.

just my 2 cents,

Robin K Panza                         panzar at carnegiemuseums.org
Collection Manager, Section of Birds          ph:  412-622-3255
Carnegie Museum of Natural History       fax: 412-622-8837
4400 Forbes Ave.
Pittsburgh  PA  15213-4008  USA

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