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Date: Thu, 30 Aug 2001 20:56:19 -0400 (EDT)
From: "T. Mike Keesey" <tmk@dinosauricon.com>
To: -PhyloCode Mailing List- <PhyloCode@ouvaxa.cats.ohiou.edu>
Subject: Clades Composed of Individuals, not Species
Here is a "rough draft" summary and elaboration of the rules Nathan Wilson
proposed on this list for defining clades with granularity at the level of
individual organisms, as opposed to the species level.
Criticism is very welcome:
1. COMMON ANCESTOR
Given: organism X
set S of 2 or more organisms
X is a common ancestor of S if and only if:
X is an ancestor of all members of S which are not X
2. MOST RECENT COMMON ANCESTOR
Given: organism X
set S of 2 or more organisms
X is a most recent common ancestor of S if and only if:
X is a common ancestor of S
and
no descendant of X is a common ancestor of S
3. LINEAGE MEMBER
(I couldn't think of a better term for this -- please let me know if there
is one.)
Given: organism X
set S of 1 or more organisms
X is a member of the lineage of S if and only if:
X is a member of S
or
X is an ancestor of one or more members of S
4. NODE-BASED CLADE
Given: organism X
set S of 2 or more organisms
X is a member of the node-based clade specified by S (Clade(S)) if and
only if:
X is a most recent common ancestor of S
or
X is descended from a most recent common ancestor of S
5. STEM-BASED CLADE
Given: organism X
set I of 1 or more organisms
set E of 1 or more organisms
X is a member of the stem-based clade internally specified by I and
externally specified by E (Clade(I <-- E)) if and only if:
no most recent common ancestor of I is an ancestor of any member
of E
and
X is not a member of the lineage of E
and
X is a member of I
or
X is an ancestor of one or more members of I
or
some common ancestor of I + X is not a member of the lineage of E
6. APOMORPHY-BASED CLADE
Given: organism X
organism I
character M
X is a member of the apomorphy-based clade specified by M and I (Clade(M
in I)) if and only if:
X is I
or
a common ancestor of X + I possesses M
and
all descendants of that ancestor which are also an ancestors of I
possess M
or
no descendant of that ancestor is an ancestor of I
(Are those last two parts necessary? Not sure....)
_____________________________________________________________________________
T. MICHAEL KEESEY
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