[Taxacom] A Cladist is a systematist who seeks a natural classification

[Richard Zander]

John:
You question even the questioners. This is good.

So, responses:

JG: "Consider the scenario of one species generating four descendant species. First off, cladists cannot conceive or countenance such an idea." My understanding is that the theorized origin is not relevant to examining relationships

RZ: Correct. You are a cladist.

JG: "Molecular analysis can give you dichotomous trees of these taxa," Not always. Molecular analyses can give unresolved branching as well.

RZ: Can give you, can, as in it’s possible. Unresolved branching comes off an unknown, unknowable, uncharacterized, presumed ancestral taxon. Magic? Partially resolved branching comes off more than one unknown, unknowable, uncharacterized, presumed ancestral taxa. More magic? Certainly even less parsimonious.

JG: "Cladistic analysis has abandoned evolutionary theory and is stuck in a structuralist hole." My understanding of cladistic analysis is that it is a method of pattern analysis. What one makes of the relationships is a separate matter. If it is so defunct then no doubt some other method will take over.

RZ: What pattern? Cladistics does not model evolutionary patterns, it analyzes the pattern (dichotomous tree) imposed by the analytic software. Cladistics does cluster taxa sort of in somewhat evolutionary relationships. This was an advance 30 years ago. You say “If it is so defunct then no doubt some other method will take over.” I’m trying. I’m trying.

Richard



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Richard H. Zander
Missouri Botanical Garden – 4344 Shaw Blvd. – St. Louis – Missouri – 63110 – USA
richard.zander at mobot.org<mailto:richard.zander at mobot.org>
Web sites: http://www.mobot.org/plantscience/bfna/bfnamenu.htm and http://www.mobot.org/plantscience/resbot/

From: John Grehan [mailto:calabar.john at gmail.com]
Sent: Monday, April 09, 2018 9:36 AM
To: Richard Zander
Cc: Stephen Thorpe; taxacom
Subject: Re: [Taxacom] A Cladist is a systematist who seeks a natural classification

Some comments, but with the caveat that these are made with full appreciation of my ignorance on systematics (I know, I know, if so ignorant why say anything at all? Inflated ego I suppose)

"Consider the scenario of one species generating four descendant species.
First off, cladists cannot conceive or countenance such an idea."

My understanding is that the theorized origin is not relevant to examining relationships

"What happens is that a cladogram based on morphological data commonly shows either a multification from an unknown shared ancestor of all taxa, or an entirely or partially "resolved" tree of dichotomous relationships. These trees are hypotheses of what?"
Hypotheses of relationship that are not fully resolved. But that is not to say that further resolution is necessarily possible (i.e. a multicotomy may represent the actual origin)
"Molecular analysis can give you dichotomous trees of these taxa,"

Not always. Molecular analyses can give unresolved branching as well.

"Cladistic analysis has abandoned evolutionary theory and is stuck in a structuralist hole."

My understanding of cladistic analysis is that it is a method of pattern analysis. What one makes of the relationships is a separate matter. If it is so defunct then no doubt some other method will take over.

I'm open to other approaches if they make sense to me (and I can comprehend their principles). For now cladistics works for me for morphology (but appreciating that there are molecular systematists out there who argue that Hennig's type of morphological cladistics is not true cladistics where one only analyzes patterns of derived character relationships within the ingroup).

John Grehan


On Mon, Apr 9, 2018 at 10:03 AM, Richard Zander <Richard.Zander at mobot.org<mailto:Richard.Zander at mobot.org>> wrote:
Perhaps one should examine what a cladistic hypothesis really is. I think such is an attempt to wrench evolutionary relationships between species into a dichotomous tree with relationships between unknown shared ancestors.

Consider the scenario of one species generating four descendant species.

First off, cladists cannot conceive or countenance such an idea. What happens is that a cladogram based on morphological data commonly shows either a multification from an unknown shared ancestor of all taxa, or an entirely or partially "resolved" tree of dichotomous relationships. These trees are hypotheses of what?

Molecular analysis can give you dichotomous trees of these taxa, all species derived from a postulated four additional unknown shared ancestors, because the species are probably generated from one progenitor species at different times. This means what? What is the hypothesis?

Cladistic analysis has abandoned evolutionary theory and is stuck in a structuralist hole. This sort of hierarchical cluster analysis is 30-year old technology. As millennials say, "It's so yesterday."


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Richard H. Zander
Missouri Botanical Garden – 4344 Shaw Blvd. – St. Louis – Missouri – 63110 – USA
richard.zander at mobot.org<mailto:richard.zander at mobot.org>
Web sites: http://www.mobot.org/plantscience/bfna/bfnamenu.htm and http://www.mobot.org/plantscience/resbot/

-----Original Message-----
From: Taxacom [mailto:taxacom-bounces at mailman.nhm.ku.edu<mailto:taxacom-bounces at mailman.nhm.ku.edu>] On Behalf Of Stephen Thorpe
Sent: Saturday, April 07, 2018 10:27 PM
To: taxacom; Kenneth Kinman; Elena Kupriyanova
Subject: Re: [Taxacom] A Cladist is a systematist who seeks a natural classification