Re: NANFA-L-- A Deluge of Snakeheads

dlmcneely at
Wed, 12 Oct 2005 10:15:12 -0500

Todd, I don't know whether there are unexploited resources in the
Potomac or not. If so, I expect that any unexploited food resources
are at lower trophic levels. However, my reading and analysis of
available information concerning resource exploitation patterns
generally suggest to me that I should use the term "niche' for
properties of a population of organisms. That restricts me (not
necessarily you) from speaking of a "vacant niche." Since the
population and not the environment has a niche, rather than the
population exploiting an existing niche, it carves its niche out of the
available resources, whether previously exploited or not. Thus,
no 'vacant' niche ever does or can exist. If one population has greater
powers to exploit particular resources than do other populations in a
given environment, then it will competitively exclude those other
populations. If not, then the other populations will (usually)
competitively exclude it. What happens with snakeheads and
ecologically similar species in the Potomac remains to be seen.

With all the new data (last two decades) coming in concerning
predators, and especially with the effects of introduced predators,
then one might predict that effects on prey species might be as great
or greater than effects on potential competitors (ecologically similar
species), even in non-island environments. Look at the consequences
for prey species of wolf re-introduction to the greater Yellowstone
ecosystem. Elk and deer have modified their forage patterns
considerably -- in other words, their niches have shifted in response
to the "new" (to the populations there now) predator.

Respectfully, Dave

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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