Continuity, reticulation, and classification

Thomas DiBenedetto tdibenedetto at OCEANCONSERVANCY.ORG
Wed Jul 25 15:26:49 CDT 2001


-----Original Message-----
From: Ken Kinman [mailto:kinman at HOTMAIL.COM]
A paraphyletic group (called "grade", especially by cladists who don't like
them)...
-------
This is rather backwards, and wrong. The term "grade" was used extensively
by Mayr and Simpson to refer to their groupings, and they rather resented
the cladists who came along much later and used the term "paraphyly" to
refer to some of those groups. Please refer to my recent posting in which I
attempted to explain the different intellecual frameworks from which these
two terms derived. One is a tree-based, systematic term (paraphyly), the
other derives from evolutionary biology and refers to levels of evolutionary
progress.
But even more fundamentally:
Not all grades are paraphyletic. Birds are a grade and are monophyletic.
Reptiles without birds are a grade and paraphyletic. The two words are not
synonymous.
In fact most of the paraphyletic groups that one encounters in
classifications
result not from a conscious grade-justified decision, but merely from an
error in analysis. They are paraphyletic, but were not necessarily grouped
together because of a judgement that they exclusively occupied the same
level of evolutionary advancement.

Tom DiBenedetto




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