[Taxacom] Reptilia (and Hominidae)

[Richard Zander]

Rank counts. There are only two ways to signal information in
classifications, and those are rank and groupings. Enforcing monophyly
limits rank as an informational metric.

The nature of bifurcating trees means that an autophyletic lineage (e.g.
polar bears) is more closely related to one part of the paraphyletic
taxon (e.g. one molecular lineage of brown bear) than to another (the
other molecular lineage. Thus, if the molecular lineages of brown bear
were named, the polar bear would be a form of a subspecies. Headline: A
Form of Brown Bear Extinct Across Arctic! This seems no big deal. If
this were an ecologically important species of another taxon it would
signal nothing to the public, to evolutionists, to biogeographers, to
diversity specialists unless they were specialists. What if chimps were
paraphyletic? Would it be important if the extinct form were forma
sapiens or not? Rank matters.

The autophyletic cactus family is more closely related to one portion of
the paraphyletic portulaca family than to another. If the two parts of
the portulaca family were named as subfamilies, then the cacti would be
a tribe, but if the two parts of the portulaca family had no real
distinction then the cacti would have no rank at all.

Your solution, Neil, is I think a third alternative to naming
autophyletic groups at an appropriate rank or strict monophyly, but it
is contrary to both phylogenetic and evolutionary taxonomy practice from
what I understand of it. Can you give an example?

*****************************
Richard H. Zander 
Voice: 314-577-0276
Missouri Botanical Garden
PO Box 299
St. Louis, MO 63166-0299 USA
richard.zander at mobot.org
Web sites: http://www.mobot.org/plantscience/resbot/
and http://www.mobot.org/plantscience/bfna/bfnamenu.htm
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-----Original Message-----
From: taxacom-bounces at mailman.nhm.ku.edu
[mailto:taxacom-bounces at mailman.nhm.ku.edu] On Behalf Of Neil Bell
Sent: Tuesday, March 17, 2009 12:02 PM
To: Taxacom at mailman.nhm.ku.edu
Subject: Re: [Taxacom] Reptilia (and Hominidae)

I think it's odd that in all of this lengthy and interesting discussion
about monophyly vs. paraphyly in classifications no-one has mentioned
rank. Isn't rank clearly the issue, rather than monophyly vs. paraphyly?
Nearly all of the cited cases of evolutionary information being "lost"
in monophyletic classifications are where a highly distinctive 
monophyletic group is derived from within another monophyletic group,
the remaining members of which are recognisable by possession of a suite
of plesiomorphic characters and have traditionally been recognised as a 
taxon. Clearly the ideal solution is to name the larger group (including
the derived clade), and to also name the derived clade, without then
being required to name the otherwise unremarkable sister group of the
derived clade (and probably other groups as well) because the larger and

smaller groups are of different rank.