Re: Not a taxonomist!
- To: s*@MAELSTROM.STJOHNS.EDU
- Subject: Re: [SG] Not a taxonomist!
- From: P* H*
- Date: Tue, 1 Feb 2000 21:47:26 EST
In a message dated 02/01/2000 6:47:27 AM Central Standard Time,
jshields@INDY.NET writes:
<<
Actually, as a retired biochemist, I am most sympathetic to the current
trend in taxonomy of using DNA sequences to develop molecular phylogenetic
trees. Now that is something about taxonomy that finally makes sense!>>
Jim, while I agree that the use of DNA and RNA is a very positive
contribution in classification, it is still not perfect.
Interpretation can be somewhat arbitrary and subjective, plus a number of
unproven assumptions have to be made.
Genetic variation does not necessarily translate into morphological variation
or relatedness.
Example-Trillium populations can have relatively large genetic variation but
by looking at the plants you could not tell one population from the other.
While some plants may be almost identical genetically but be very divergent
in morphology.
Some relationships are based on mutation rates, but this assumes that the
rate of mutation over time has been consistent, which of coarse is just an
assumption.
Other assumptions are based on gene frequencies which begs the question.
Since there is no known cause for Microevelution, only assumptions and much
debate.
Even at the adaptive phase of evolution questions remain and Biologists will
fight tooth and nail with each other over which module is correct. (genetic
drift or genetic revolution)
I think that it's safe to say that on the species level Morphology has been
highly successful at phylogenetic relationship identification. The same at
the genus level but not as high a success rate, The problems come in at the
order level and above.
The place I think that DNA and RNA testing plays an important role is in the
differation of species and genera do to polyploidy, otherwise the duplication
of chromosomal material In which expression is effected by unique gene
combinations and cross linkage.
Paul
