Real taxa => Ranking

[Robin Leech]

 I just love it.  The application of an arbitrary decision give objectivity.
Robin Leech

----- Original Message -----
From: "Peter Stevens" <peter.stevens at MOBOT.ORG>
To: <TAXACOM at LISTSERV.NHM.KU.EDU>
Sent: Tuesday, September 28, 2004 12:13 PM
Subject: Re: Real taxa => Ranking


> >Certainly for flowering plants age is not a workable criterion for
> >ranking - just read the vast literature on aging nodes, with
> >estimates varying sometimes very considerably indeed.  But if we had
> >a well-supported tree to the nodes of which we could assign ages in
> >an unproblematic fashion, then we could arbitrarily decide on the
> >ranks to be assigned to particular slices of time....  So the
> >objectivity comes in the application of what is ultimately an
> >arbitrary decision.
>
>
> P.
>
>
>
> >I was surprise to read:
> >
> >How to select the "appropriated" taxonomical rank (genera, tribe etc)
> >for a
> >group is a matter of debate, mainly because this issue is out of the
> >scope
> >of the formal methods of systematics (cladistics).
> >
> >====================
> >
> >When Willi Hennig himself clear proposed an objective method of ranking
> >years ago as part of his "Phylogenetic Systematics" [= ? cladistics at
> >one time, but today Willi would not recognize what we are calling
> >"cladistics" has having any relationship to his idea, etc.]
> >
> >Hennig simply stated the proper criterion for rank was age of the
> >taxon. And he suggested once one had their preferred cladistic
> >hypothesis / tree, then there were various other methods which then
> >could be used to date the taxa within the hypothsis / tree. He suggested
> >various date for the categories of the Linnaean hierarchy, like 100 MYA
> >or late cretaceous origin for the family category.
> >
> >Obviously Huxley who placed Homo sapiens in the Kingdom Psychozoa
> >objected as did virtually everyone else. And apparently after that all
> >was forgotten, but ...
> >
> >So, objective methods of ranking are only "out of the scope of the
> >formal methods of systematics (cladistics)" for those who do not want
> >them.
> >
> >Oh, well ...
> >
> >
> >
> >F. Christian Thompson
> >Systematic Entomology Lab., USDA
> >c/o Smithsonian Institution
> >MRC-0169 NHB
> >PO Box 37012
> >Washington, DC 20013-7012
> >(202) 382-1800 voice
> >(202) 786-9422 FAX
> >cthompso at sel.barc.usda.gov e-mail
> >www.diptera.org  web site
>