Re: Not a taxonomist!

Hi Cindy,

A "molecular phylogenetic tree" is a "phylogenetic tree" based mainly on
molecular information (i.e., structures of DNA molecules) rather than the
historical approach using just morphological in formation.  Here,
"morphology" means the physical structure(s) of the plants.

A phylogenetic tree is just a family tree in broad outlines.  I have a
crude one, copied from a published paper by Mark Chase at RBG Kew and a
host of his co-workers around the world, posted at:

http://garden.dmans.com/amaryllids/tree.html

which incidentally needs to be updated based on more recent results
published by Alan Meerow and Mark Chase and others.

The intent of phylogenetic trees is to show the genetic relatedness of the
plants connected in the "tree."  This is done in the case of DNA by
determining the nucleotide base sequences for homologous genes in a series
of species and then comparing these statistically to calculate their
"distances" from each other.  The tree diagram is constructed using these
distances.

This is a complicated process, and while not absolute is much more rigorous
than the old way using only physical structure.  This molecular approach is
less subjective.  The results from the older approaches contained a large
subjective component, and the amazing thing might seem to be that
conclusions from the molecular data are often very close to the conclusions
arrived at more subjectively.  The value of the molecular approach is that
when its conclusions disagree with those of the older method, we have
learned something new.  When the two methods produce similar conclusions,
the results based on the older methods are thereby confirmed.

Jim

At 08:34 AM 2/1/00 EST, you wrote:
>
>OK Jim, I have to ask....
>What are molecular phylogenetic trees?  and can you have m.p.flowers too??
>Thank you,
>Cindy Johnson
>
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