Species III

[Ron Gatrelle]

Michael Gochfeld wrote:
Like Norbert I remain to be convinced that genetic distance (represented as
percent) means the same thing in different taxa (or for that matter in
diffrerent fragments of the same two taxa).

Norbert Kondla wrote:
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.
___________

    Pterourus rutulus and P. eurymedon have the same mtDNA sequence. Yet
they
are obviously sympatric (co-occurring) species. This tells me that mtDNA
analysis is just about worthless relative to these two species.  It has
recently been determined that Phyciodes batesii batesii and P. b.
maconensis are "very different" in their mtDNA. Yet this does not yet
release one to say that batesii batesii and maconensis are in fact two
species.  How many variables are there just like and in-between these
extremes that _have_ been put forth to us as the Holy Grail final word on
if X is a species or subspecies?  Quite a bit I bet.
    What is going to happen when someone accidentally puts two chemically
identical (or almost so) critters that live a long way from each other -
and by chemical analysis have been "proven" to be the "same" species -
together and finds they will not mate and if they are coerced to do not
produce viable offspring?   And what will be the explanation when the two
very genetically different "species" that live a long way apart are for
some reason put together and it is found that they mate and produce
offspring like Gypsy moths?
    Genetics is not the all and all answer all at the specific and
subspecific level.
    We already know that genitalia are not the magic bullet either. In some
genera all the genitalia are basically the same. In some they vary with the
subspecific morphology.
    There are likely differing reasons that Kondla, Gochfeld and Gatrelle
all have a lack of total faith in what Norbert called the "chemical species
concept."  Perhaps others need to not just automatically swallow the whole
hook, line and sinker of those who so elevate this area/means of analysis
as the arrival point of taxonomic detecting and systematic discernment.
With this area of argument I say there is lots of subjectivity.

Ron Gatrelle






 
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