Farewell to species (but not yet!)

[Gurcharan Singh]

-----Original Message-----
From: Jong, R. de <Jong at NATURALIS.NNM.NL>


>polyphyletic group. If we agree that an orchid and an elephant have a
common
>ancestor (be it far back in history) than the group orchid+elephant is a
>group that does not include all the descendants of their common ancestor.


Extension of such interpretations destroy the very character of distinctions
between the terms monophyly, paraphyly and polyphyly. We will appreciate the
difference only if we talk in terms of "immediate common ancestor" and not
just a"common ancestor". Paraphyletic group in that sense would be very
similar to monophyletic group only that a monophyletic group includes all
descendents of the immediate common ancestor and a paraphyletic group a part
(major part including the immediate common ancestor) of these descendents.
The members that are left out would if merged with some other group of
species would make that polyphyletic because they are not carrying along
their common ancestor into the new amalgamation. The cutting rules devised
by Dahlgren and Rasmussen are very illustrative for distinction between
monophyly, paraphyly and polyphyly.

Gurcharan Singh
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Dr. Gurcharan Singh                      Res:
Department of Botany                        932 Anand Kunj
S. G. T. B. Khalsa College                  Vikas Puri
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