[Taxacom] Paraphyletic groups as natural units of biological classification

[John Grehan]

Here’s a bit of irony regarding Steven’s  assertion that “scientists in our
broad area are not so good at weighing up pros and cons and coming to a
sensible and rational decision about what to do. They just cling to ideals
..”

Hörandl & Stuessy claim that “Allopatric speciation, therefore, fits well
the cladistic model of symmetrical divergence, but this is no longer regarded
as the predominant mode of speciation, especially in plants (e.g.,
Rieseberg & Brouillet, 1994). I suppose Rieseberg & Brouillet have proved
this in some way, but like some other similar vague referencing,  Hörandl &
Stuessy don’t bother to say how.



Hörandl & Stuessy then say “ Other evolutionary processes, especially
budding and merging, enhance asymmetrical divergence and therefore
occurrence of paraphyly.


*“Budding. ..* obvious are cases of peripatric speciation after
geographical isolation of a small group of populations. This is expected to
happen mostly after colonizing events by a few individuals, then followed
by rapid speciation and adaptation to new environments. Recent evidence
from biogeographical studies on both animals and plants suggests that
peripatric speciation may be more common than previously thought, since
dispersal, even transoceanic dispersal, explains many disjunct
distributional patterns.



For this claim they cite several papers de Queiroz, 2005; Knapp & al.,
2005; Harbaugh & al., 2009; Schaefer & al., 2009; Emadzade & Hörandl, in
press; Emadzade & al., in press). I have only read de Queiroz and that
paper is based on the fiction that molecular divergence estimates are
maximal or actual. If the other papers present similar assertions than the
claim that allopatry is not the predominant mode of differentiation then
the claim itself is a fiction.



John Grehan

On Fri, Sep 26, 2014 at 6:31 PM, Stephen Thorpe <stephen_thorpe at yahoo.co.nz>
wrote:

> Ken (and list):
> Let's face it, a large proportion of the systematics/taxonomic community
> clings to monophyly like a baby to its mother's breast! It is so ingrained
> that it is probably impossible to shift. As with everything, the idea of a
> strictly monophyletic classification has its pros and cons. The main cons
> seem to be (1) instability of classification, resulting from the fact that
> determining monophyletic groups is evidence based science, subject both to
> changes resulting from additional data, and from subjective differences in
> the evaluation of evidence; and (2) one tends to be left with a
> paraphyletic residue which is just too hard to crack. There are only two
> options for forcing these residues to be monophyletic. Either (1) just
> recognise the wider monophyletic group and don't recognise any of the
> included monophyletic groups (e.g. recognise reptiles, but not birds); or
> (2) split up the residue into trivially monophyletic groups (maybe down to
> single species).
>  The problem with (1) is obvious. The problem with (2) is that you end up
> with far too many monotypic higher groups which don't really differ
> diagnostically from each other except in as much as the species can be
> distinguished. In my experience, scientists in our broad area are not so
> good at weighing up pros and cons and coming to a sensible and rational
> decision about what to do. They just cling to ideals ...
> Stephen
>
> --------------------------------------------
> On Fri, 26/9/14, Kenneth Kinman <kinman at hotmail.com> wrote:
>
>  Subject: [Taxacom] Paraphyletic groups as natural units of biological
> classification
>  To: "taxacom at mailman.nhm.ku.edu" <taxacom at mailman.nhm.ku.edu>
>  Received: Friday, 26 September, 2014, 12:52 PM
>
>
>
>
>  Dear All,
>             I was just
>  rereading a 2010 paper by Horandl and Stuessy (published in
>  the journal Taxon).  It should be required reading in
>  any systematics course.  Below is the abstract.
>
>      --------------------Ken
>
>
>
>
>
>  Hörandl, E. & Stuessy, T.F.  2010.
>  Paraphyletic groups as natural units ofbiological
>  classification.  Taxon 59: 1641-1653.
>
>  ABSTRACT:
>  Despite the broad acceptance of phylogenetic principles in
>  biologicalclassification, a fundamental question still
>  exists on how to classifyparaphyletic groups. Much of the
>  controversy appears due to (1) historicalshifts in
>  terminology and definitions, (2) neglect of focusing on
>  evolutionaryprocesses for understanding origins of natural
>  taxa, (3) a narrow perspective ondimensions involved with
>  reconstructing phylogeny, and (4) acceptance of lowerlevels
>  of information content and practicability as a trade-off for
>  ease ofarriving at formal classifications. Monophyly in
>  evolutionary biology originallyhad a broader definition,
>  that of describing a group with common ancestry.
>  Thisdefinition thus includes both paraphyletic and
>  monophyletic groups in the senseof Hennig. We advocate
>  returning to a broader definition, supporting use
>  ofAshlock's term holophyly as replacement for monophyly
>  s.str. By reviewingprocesses involved in the production of
>  phylogenetic patterns (budding, merging,and splitting), we
>  demonstrate that paraphyly is a natural transitional stage
>  inthe evolution of taxa, and that it occurs regularly along
>  with holophyly.
>  When a new holophyletic group arises, it usually coexists
>  for some time with itsparaphyletic stem group. Paraphyly and
>  holophyly, therefore, representrelational and temporal
>  evolutionary stages. Paraphyletic groups exist at alllevels
>  of diversification in all kingdoms of eukaryotes, and they
>  havetraditionally been recognized because of their
>  descent-based similarity. Wereview different methodological
>  approaches for recognition of monophyleticgroups s.l. (i.e.,
>  both holophyletic and paraphyletic), which are essential
>  fordiscriminating from polyphyly that is unacceptable in
>  classification. Forarriving at taxonomic decisions, natural
>  processes, information content, andpracticability are
>  essential criteria. We stress using shared descent as
>  aprimary grouping principle, but also emphasize the
>  importance of degrees ofdivergence plus similarity
>  (cohesiveness of evolutionary features) as
>  additionalcriteria for classification.
>
>
>
>
>
>
>
>  _______________________________________________
>  Taxacom Mailing List
>  Taxacom at mailman.nhm.ku.edu
>  http://mailman.nhm.ku.edu/cgi-bin/mailman/listinfo/taxacom
>  The Taxacom Archive back to 1992 may be searched at:
> http://taxacom.markmail.org
>
>  Celebrating 27 years of Taxacom in 2014.
>
> _______________________________________________
> Taxacom Mailing List
> Taxacom at mailman.nhm.ku.edu
> http://mailman.nhm.ku.edu/cgi-bin/mailman/listinfo/taxacom
> The Taxacom Archive back to 1992 may be searched at:
> http://taxacom.markmail.org
>
> Celebrating 27 years of Taxacom in 2014.
>