Message 2000-09-0005: RE: Nathan Wilson's question

Wed, 27 Sep 2000 14:01:10 -0400

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Date: Wed, 27 Sep 2000 14:01:10 -0400
From: "Moore, Gerry" <>
To: 'Philip Cantino' <>
Subject: RE: Nathan Wilson's question

PC: Nathan is concerned about the effect of interclade genetic transfer
on clade nomenclature. [...]  I don't think this is a problem if one
accepts that a species may belong to two non-nested clades. [...] There is
nothing in the PhyloCode that prohibits naming a clade, some species of
which belong to another non-nested clade [...].

  I actually see the issue that Nathan Wilson brought up as potentially
being problematic, since a species that may eventually be shown to belong to
multiple nonnested clades may be used in phylogenetic definitions (as a
specifier) _prior_ to the knowledge that the species actually belonged to
more than one nonnested clade.  
  For example, let's say Clade Z is defined as the least inclusive clade
containing species 3 and species 4. Species 3 is then shown to have
originated through the hybridization between species in Clade A and Clade B.
When the definition was originally formulated it was believed that species 3
was a member of only Clade A (not B) and the circumscription of Clade Z was
exclusive of Clade B.  Doesn't the circumscription of Clade Z have to
include all nonnested clades to which each specifier (see Art. 11.1) is a
member (i.e.,  the circumscription of Clade Z will have to be expanded to
include Clade B to accommodate specifier Species 3 being a member of the
nonnested Clades A and B)?
  Thus (expanding this logic to LGT cases), wouldn't it be hard to apply
phylogenetic nomenclature (without running the risk of having a lot of
circumscriptional changes) to the prokaryotes where so much new information
on lateral (horizontal) gene transfer is being and remains to be discovered?

Gerry Moore
Research Taxonomist
Brooklyn Botanic Garden
27 Sep. 2000     


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