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  Re: Lemna and other duckweeds
From: "Eduardo Goncalves" edggon at hotmail.com> on 2000.06.22 at 02:39:02(4885)
Dear Jim,

Yes, you're correct. Let me try to say it with more precison: If you
consider that all taxa are a somewhat stable assembly of genes that were
transfered mainly in a "vertical" way in recent times, the best hypotesis we
have now for the duckweeds is that they are very specialized forms of the
assembly of genes we use to call aroids. They share very similar sequence of
cpDNA genes we suppose that are homologous and they are also very similar if
we compare the effect of restriction enzimes at the total DNA (nuclear +
plastid). Since we don't know any other thing that could be considered
better than DNA to show relationship without "morphogenetic black boxes",
all this evidence make us believe that aroids+duckweeds can be considered a
good taxonomic group together. I know there are lots of strong limitations
(like reticulation, lost genetic information, possibility of "lamarckist
genes", horizontal transference, etc), but I think it is the best
information we have. Maybe, in the future, we will be able to travel back in
the time and see different stages of evolution of the Araceae. Maybe we will
discover that we will never now the true story of evolution (because it is
unique and most evidences are lost) so the taxonomy will be deliberately
artificial! (Hey, that will be really good... For the first time after
Darwin's era, we will be able to be sure about our taxonomic concepts). Ok,
I think I can't be more precise than this by now. I still can refine my
concepts, but my poor English is already lacking! Maybe if I could write in
Portuguese... :o)

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