Re: NANFA-L-- Moribund fish & Life Outside

dlmcneely at
Wed, 26 Oct 2005 09:52:08 -0500

In theory, it is the maintenance of evolutionary independence that
defines a species in modern context, and not whether or not alleles
make it from one population to another. In other words, an allele that
enters a population may or may not persist and contribute to the
adaptive future of that population. If it does, then the source
population might be part of the evolutionary lineage in the species
sense. If it doesn't, then the two populations are independent. So --
in Galapagos finches, hybridization is normal when there is a
bottleneck due to drouth or other environmental crunch, but the hybrids
fall out of the mix when better conditions arise. Stream minnow
hybrids are not unusual, but they usually contribute little to later
generations. Lepomis? Well, the parent populations persist,
maintaining their integrity.

For a while, it was fashionable in some circles to define species
strictly on the basis of multivariate statistical results on
morphological variation (numerical taxonomy). I don't know whether
what the systematicists do now is more or less congruent with what
evolution does compared with numerical taxonomy, but the current crop
of systematicists seems more comfortable with their current methods.

The arbitrariness of numerical taxonomy, though completely
misunderstood by creationists, sort of made a hit among them at one

So far as acceptance of published systematics results and conclusions,
the fact that some of us are behind in our reading and assimilation
doesn't alter what's going on in nature. I work with some folks here
who still refer to Oklahoma populations of Luxilus cardinalis
as "duskystripe shiners," and my dissertation advisor, though not
behind in his reading and assimilation, still insists on placing Ozark
minnow in Notropis. But neither of those situations alters what
happened and is happening in terms of genes, adaptation, and
evolutionary history (which I don't profess to know, but some do).

Did someone once say that the species is a "real evolutionary entity,"
while someone else said that "organisms evolve at the population level,
and we make up names in order to communicate how little we know about
the process?"


David L. McNeely, Ph.D., Professor of Biology
Langston University; P.O. Box 1500
Langston, OK 73050; email: dlmcneely at
telephone: (405) 466-6025; fax: 405) 466-3307
home page

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