Species definitions!

[Kondla, Norbert FOR:EX]

I really do feel guilty about being so unusually mouthy today but gosh, the
postings have been too interesting to let sleeping dogs lay :-) Further to
the multitude of explicitly defined species concepts I have noticed two
species concepts that some people have used, seemingly without even knowing
that they are doing so. One is what I call the genitalic species concept,
wherein some people take plainly different looking butterflies living in
different places and even on different continents, look at the genitalia
(sometimes not very carefully) and then pronounce them to be one species.
Bogus logic at best and junk science at worst :-). Another is what I call
the chemical species concept. Looking at the chemistry of selected gene
segments is growing increasingly fashionable. Certainly gene chemistry, like
genitalia, can provide some potentially useful data but there is always room
for interpretation. The chemical species concept might argue that two
butterflies with, for example, less than 3% difference in gene chemistry are
the same species. Extending this logic to mammals would result in
chimpanzies and humans being declared the same species. I have some
difficulty accepting that there is some magic level of similarity in gene
chemistry that defines what is or is not a species.

-----Original Message-----
From: Kenelm Philip [mailto:fnkwp at aurora.alaska.edu]
Sent: Wednesday, September 05, 2001 2:15 PM
To: leps-l at lists.yale.edu
Subject: Re: Species definitions!



> Are there, and do we know - that plants and animals are different?

What about the single-celled organisms that may, or may not, contain
chlorophyll? Back when there were only two kingdoms, it was totally unclear
as to whether these were plants or animals. The hypothetical  3 year old
might have a bit of trouble dealing with five kingdoms, let alone the
Woese system of domains with _lots_ of kingdoms.

> How about moths and butterflies?  Does a 7 year old know they are
> different? If so, then the rank of Suborder is evident to him/her even
> though they likely do not know the terms Heterocera/Rhopalocera.

The Heterocera/Rhopalocera split is outmoded taxonomy, since Heterocera
do not form a monophyletic group. And note that the family Hedylidae now
is included in the Rhopalocera, although they do not have clubbed antennae,
and are not primarily diurnal--thus causing a problem for the hypothetical
7 year old.

	As far as the concept of species goes, we have a number of differ-
ent and incompatible species concepts wandering around. Most of us were pre-
sumably brought up on the BSC (biological species concept), according to
which reproductive isolation is the key factor involved. Before that there
was what one might call a morpholgical species concept. However, we cur-
rently have the phylogenetic species concept (PSC), a close relation of the
ESC (evolutionary species concept). See Zink & McKitrick: 'The Debate over
Species Concepts and its Implications for Ornithology'. The Auk 112(3):701-
719, 1995. These concepts will yield different breakdowns of organisms
into species--a problem which may appear in the courts as more laws and
regulations are keyed to species, with respected taxonomists arguing for
both sides of various issues.

	The trouble is that taxonomy is not simple, nor free from contro-
versy. And the controversies will not be solved by appealing to the abil-
ities of young children who are unaquainted with the full diversity to
be found within any group of organisms.  :-)

							Ken Philip
fnkwp at uaf.edu




 
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