[Taxacom] Paraphyletic groups as natural units of biological classification

Richard Zander Richard.Zander at mobot.org
Sat Oct 4 11:12:53 CDT 2014


Gee, I been away and missed all the good arguing!

Cladistics cannot demonstrate monophyly.  

Example:

(your mum, you) = phylogenetic relationship
your mum -> you = monophyly

"Paraphyly" is a cladistic word referring to cladograms. Since cladograms cannot demonstrate monophyly, the argument is empty.


-------
Richard H. Zander
Missouri Botanical Garden – 4344 Shaw Blvd. – St. Louis – Missouri – 63110 – USA
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] On Behalf Of Stephen Thorpe
Sent: Saturday, September 27, 2014 10:30 PM
To: Curtis Clark; taxacom at mailman.nhm.ku.edu; AlanWeakley
Subject: Re: [Taxacom] Paraphyletic groups as natural units of biological classification

But this example doesn't illustrate the terms of the debate, as I see it. As you describe the example, we have a rare case of an uncontroversial and fully determined monophyletic classification of flowering plants which leaves (no pun intended!) no paraphyletic residue. Examples of this kind are rare, I suggest, and the typical case involved only moderately supported phylogenies and a basal paraphyletic residue that is too hard to crack.

Stephen

--------------------------------------------
On Sun, 28/9/14, Weakley, Alan <weakley at bio.unc.edu> wrote:

 Subject: Re: [Taxacom] Paraphyletic groups as natural units of biological classification
 To: "Curtis Clark" <lists at curtisclark.org>, "taxacom at mailman.nhm.ku.edu" <taxacom at mailman.nhm.ku.edu>
 Received: Sunday, 28 September, 2014, 3:09 PM
 
 Here seems to be
 "the thing".  
 
 The "basal angiosperms" or
 "primitive dicots" or "ANITA and the
 Magnoliids" or...  are clearly a basal grade to other  angiosperms, based on all recent analyses.  Amborellales  sister to all other angiosperms.  Then Nymphaeales sister  to all the rest, then...  ETC.  Whether you have access to  all the papers, a good summary of the current consensus can  be had online at the Angiosperm Phylogeny Website, at MoBot,  compiled by Peter Stevens.  This clearly shows a grade of  various orders (all small, currently) and then also the  magnoliids (mostly small, currently, except especially, the  Lauraceae and somewhat less so the Piperaceae).
 
 So, the "basal
 angiosperms" are not monophyletic.  And yet, it is  "useful" and "convenient" to refer to  them as a group -- to classify them as a unit.  In  teaching, and in floras (Flora of Virginia 2012, Flora of  the Southern and Mid-Atlantic States 2014)), it is  "handy" ("useful") to divide the  vascular flora into:  Lycophytes, Ferns, Basal Angiosperms,  Monocots, and Eudicots.  It seems  "disproportionate" to treat 4 or more units  (small, currently, a genus or two, a hundred species or  less, each) at equivalent rank to Monocots or Eudicots,  which have many more orders, families, genera, and  species.  Especially, as their morphological  differences  seem relatively obscure, abstruse, and non-obvious.  If the  morphological distinctions were completely obvious, maybe we  would be more accepting -- no-one seems to have a hard time  with Ginkgo or Welwitschia as (modern) monotypes:  uncontroversial monotypic orders.  
 
 So, Judd et al., for instance, in their  textbook, Plant Taxonomy: a Phylogenetic Approach, use  quotes to indicate units that are not monophyletic but yet  are "useful".  There is an interesting tension  here between "strict monophyly" and  "intuitive (useful) classification  units".   Units with quotes seem to flag  something like "this is not monophyletic but sure is  handy so we will keep using it informally".
 
 I'm not taking sides here
 (I am conflicted).  But...  it may be instructive to  contemplate that other "intuitive (useful)  classification units" ("plants",  "animals", "algae", "fungi",  "birds", "bacteria",  "slime-molds", ) have fared increasingly poorly  over time as real classification units.  I was taught as a  college botany student in the 1970s that there were 2 main  types of algae (a kind of plant):  prokaryotic  ("blue-green algae") and eukaryotic (green, red,  brown, etc., algae) --  several decades on, this looks  laughable (and in no way "useful" or  "convenient" in any respect).  On the other hand,  the "Basal Angiosperms" seem a "useful"
 unit for teaching and organization and classification, even  if monophyly is uncertain or even disproved...  
 
 -----Original Message-----
 From: Taxacom [mailto:taxacom-bounces at mailman.nhm.ku.edu]
 On Behalf Of Curtis Clark
 Sent: Saturday,
 September 27, 2014 9:29 PM
 To: taxacom at mailman.nhm.ku.edu
 Subject: Re: [Taxacom] Paraphyletic groups as  natural units of biological classification
 
 On 2014-09-27 6:59 AM, John
 Grehan wrote:
 > Since you have some
 expertise and strong opinions on paraphyly I  > presume you have read the citation of  Stuessy (2010) on basal  > angiosperms  being a paraphyletic group. As I do not have immediate  > access to that paper perhaps you could  describe in what way that group was paraphyletic.
 
 Some of its members
 (Austrobaileyaceae?) are more closely related to the rest of  the angiosperms than others are. (Same definition as
 usual.)
 
 --
 Curtis Clark        http://www.csupomona.edu/~jcclark  Biological Sciences
    +1 909 869 4140
 Cal Poly
 Pomona, Pomona CA 91768
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