In fooling around with PCR analysis I recall asking the question as to "can
it tell me that we are dealing with different species?" I was looking at a
beetle that some how was able to feed on over 355 different species of
plants (many are unrelated plant species). I suspected that there was
really a species complex involved and wanted to look into this problem via
PCR. I was told that there was no criteria set for differentiating between
species (after all a species is an artificial taxon developed to help us
"pidgeon hole" groups of related organisms". I suppose it made sense at
least in dealing with insects and differentiating between sympatric
populations of the same organisms. There could be radical differences
between the two populations genetic make up, yet have no morphological
differences. i.e. sweet potato whitefly and silverleaf whitefly. Also in
cases in which certain insects develop resistance to pesticides, etc can be
mediated by mutations of the endosymbionts, which would result in huge
differences in genetic make up (allozymes, and isozymes also I think), but
no change in morphology (endosymbiont evolution theory). Now it is
possible that there are morphological characteristics that were not
considered and as we study further we will find the characteristics that
will differentiate these cases where there are very simmilar appearing
organisms. However, on the other hand I prefer the ecological approach and
biological species concept. Of course it might not work in the cases of
sympatric species, or are they really species if naturally occuring hybrids
are formed....
MTF
>Actually most of the people I've talked to that describe new species
>have been against using DNA testing. Teeth counts, scale counts, ray
>counts, skeletal structure and in some families color are the
>standards they use. Some have said it may someday be a tool, but at
>present isn't useful. We had a thread about a year or two back (has
>this list really been around that long?) were a few folks using
>familiar with genetic testing methods, couldn't even come close to
>agreeing amongst themselves as to the best genetic test method.
>Seems many think genetic testing is a panacea for defining a species.
>While it can tell how much genetic material is in common between fish,
>how do you define how much difference there needs to be for species to
>be different species? This will still remain up to the judgement of
>the person making the determination. Which genetic test method is
>best? Again up to the individuals judgement. And now they have to
>convince the rest of the scientific community that they have a valid
>reason for defining a species by a standard the rest do not use. While
>at the same time the proponents of this method cannot agree to a
>standard test or level. It appears genetic testing has an up hill
>battle for acceptance in the science of species definition.
>
>Cary Hostrawser
>
>My Rainbowfish Home Page
>http://pw2.netcom.com/~caryho/home.html
>
>Rainbowfish Study Group Web Page
>http://home.stlnet.com/~gwlange/rainbowfish.index.html
>
Mach T. Fukada, Web Master
fukada at hawaii.edu
Honolulu Aquarium Society
http://www.geocities.com/Heartland/Meadows/2948/HASF.html