Subject: BRYONET: Pottiaceae and new new classification
Date: Wed, 29 Oct 2008 11:23:49 -0500
From: Richard Zander <Richard.Zander@mobot.org>
Reply-To: bryonet-l@mtu.edu
To: bryonet bryonet <bryonet-l@mtu.edu>
BRYONET
There has been some discussion of Pottiaceae in the past week or two on
Bryonet. Some of the questions can be solved by studious attention to
the Code. There is, however, reference to Goffinet, Buck and Shaw's
Classification of the Bryophyta, a version on the Web
<http://www.eeb.uconn.edu/people/goffinet/Classificationmosses.html>
which extends the Buck and Goffinet original classification in Bryophyte
Biology, and Goffinet and Buck's second version in Molecular Systematics
of Bryophytes.
These classifications are the result of enormous labor by seasoned
bryologists, and are of value. They are all deeply flawed, however, in
enforcing phylogenetic monophyly on portions of the classification. I
can best speak for and defend the Pottiaceae, but I note that the two
fine families, the Ephemeraceae and the Splachnobryaceae, are lumped
into the Pottiaceae, and a somewhat less distinct family, the
Cinclidotaceae, is also lumped into it. From reading the justifications
of Goffinet and Buck in Molecular Systematics of Bryophytes, this is
solely due to requiring phylogenetic monophyly (as a taxon derived from
a common ancestor and including all descendants), such that families (or
genera) cannot derive from a clade named as a different family (or
genus). That families apparently cannot evolutionarily derive from other
families is a common justification for changes in classification, ditto
genera from genera, etc. The new classification of Pottiaceae follows
molecular studies by Werner et al., cited in MSB. On the other hand
Goffinet, Buck and Shaw did recognize Pleurochaete, well known to derive
from Tortella. They did also lump Timmiella into Pottiaceae, though it
is well-known to be phylogenetically distant from the Pottiaceae. If
there is method to their decision to require phylogenetic monophyly in
some clear-cut cases of paraphyly or polyphyly and not in others, this
is not clear.
A rigid enforcement of phylogenetic monophyly is a particularly bad
problem because it hides evolutionary information. The description of a
new family (or other supraspecific taxon) is a major event in
evolutionary taxonomy, and the rejection of the name and associated
characteristic morphological traits and sometimes biorole is wrong,
simply because of an antievolution-in-classification presumption that
taxa of higher rank cannot evolve from taxa of the same rank.=20
Relevant is the continued recognition of the family Rhabdoweisiaceae. My
paper in Bryologist (111: 292-301) demonstrated that it has no
acceptable diagnosis although it forms a reliable clade just below
Dicranaceae s.str. and other families. I believe what fuels its
recognition by cladists is that: if Rhabdoweisiaceae is actually just a
minor basal lineage of Dicranaceae with other families branching off the
Dicranaceae as sister groups distally (just as there are families
derived from distal lineages of Pottiaceae), then Dicranaceae is
paraphyletic and all genera of Pottiaceae, Eropdiaceae, Calymperaceae,
and Leucobryaceae must be transferred to Dicranaceae, and the family
names placed in its synonymy. This is even more nonsensical in the
context of reflecting evolution in classification than retaining
Rhabdoweisiaceae, which has no distinguishing evolutionary importance
other than genetic isolation, but having to choose between two bad
classifications is what adherence to phylogenetic monophyly brings.
Units of macroevolution are genera and taxa of higher rank (even though
ultimately it is genetic changes in the individual that powers natural
selection or drift), and such units should reflect as best we can
ascertain the effects of history on traits that respond to evolutionary
forces, not simply patterns in the genetic continuity or isolation
demonstrated by molecular analysis. Taxonomy informs evolutionary
thought by careful description of such units (taxa are diagnosed to
reflect apparent evolutionary differences and minimize complete
convergence). The redemption of systematics faced with difficulties in
dealing with vast numbers of species and few broad methodological
guidelines is not to follow an arbitrary classificatory system that
substitutes monophyly for evolution. It must remain evolutionary
systematics, which recognizes paraphyly as a necessary result of
reflecting perceived results of evolution in classification.
Evolutionary monophyly (one taxon derived from one other) is quite
different from phylogenetic monophyly.
I urge bryologists to reject in the Goffinet, Buck and Shaw
classification all lumping and splitting that is based solely on
enforcing phylogenetic monophyly, and is not based on reasoned
evaluation of the evolutionary importance of the taxa involved. This is
not maundering for the quondam methods of evolutionary taxonomy, but
vigorous rejection of artificial, antievolution elements in the
taxonomies of pattern cladists.
A response would be welcomed.
*****************************
Richard H. Zander
Voice: 314-577-0276
Missouri Botanical Garden
PO Box 299
St. Louis, MO 63166-0299 USA
richard.zander@mobot.org <mailto:richard.zander@mobot.org>
Web sites:
<http://www.mobot.org/plantscience/resbot/>
<http://www.mobot.org/plantscience/bfna/bfnamenu.htm>
*****************************
------------------------------------------------------------------------
Bryonet is a service of the International Association of Bryologists (IAB)
and is administered by Janice Glime <jmglime@mtu.edu>
through Michigan Technological University
IAB Officers:
President Janice Glime <jmglime@mtu.edu>
Secretary Geert Raeymaekers <geert.raeymaekers@skynet.be>
Treasurer Blanka Shaw <blanka@duke.edu>
First VP: Masanobu Higuchi, Second VP: Benito Tan
To join IAB ($11 per year), contact Blanka Shaw <blanka@duke.edu>
IAB website: http://www.bryology.org/
------------------------------------------------------------------------
--
*****************************************
Dr. Janice Glime, Professor Emerita
President of IAB; Manager of Bryonet
(Michigan Technological University)
219 Hubbell St.
Houghton, MI 49931 USA
email: jmglime@mtu.edu
phone: 906-482-1610
fax: 906-487-3167
*****************************************
0 comments. Please write yours here.:
Post a Comment