[Taxacom] Paraphyletic groups as natural units of biological classification

[Stephen Thorpe]

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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