What's interesting in systematics?

Judy Stone jstone at ACPUB.DUKE.EDU
Thu Feb 27 11:28:17 EST 1997


I am not a systematist, but I am surrounded by them, and the field is far
from lethargic!  It's true that some of the most important questions would
be difficult to access without a significant investment, so I'm not sure
how well you could get across the excitement of the field within a few
hours of lecture/lab.

A lot of the excitement is methodological.  A couple decades ago, a big
debate exploded between the pheneticists, who thought that similarity would
be a good basis for classification, and the cladists, who insisted that
only shared derived characters are useful in establishing phylogenetic
relationships.  Although the cladists have won that battle, debate
continues between hard-core cladists and people who believe that other
approaches are useful.

One of the underlying reasons for discussion is that we have learned that
the rate of evolution is not constant, even for molecules.  There is no
"molecular clock".  Non-coding regions change more rapidly than coding
regions, different base pair positions in coding regions evolve at
different rates (a classic example is that synonomous positions change more
quickly than non-synonomous ones), different genes evolve at different
rates, and the rate of molecular evolution differs between taxa.  There are
different philosophical positions about what we should do about this rate
heterogeneity when we are trying to reconstruct phylogenetic relationships.

Another interesting frontier is the use of phylogenies in the comparative
method.  It is not ok to tally up species numbers having a certain trait
and make a conclusion about its adaptiveness; we need to look at the number
of times the trait has arisen on an evolutionary tree.  This has been used
to address many questions, such as whether behavior evolves more rapidly
than morphology, whether fleshy-fruitedness tends to favor the evolution of
dioecy, and coevolution between parasite/host or herbivore/plant systems.

There is also interest in using phylogenetic methods at the intraspecific
level, to address questions about speciation, dispersal, and hybridization,
just to name a few examples.   The molecular evolution of the AIDS virus is
a hot topic right now.  John Avise's text (1994, Chapman & Hall),
"Molecular Markers, Natural History, and Evolution", is a well-written
introduction to this field.

I wish I knew of a good, simple reference I could recommend for access into
the phylogenetic literature.  My exposure has been through reading the
primary literature and discussion with practicing systematists.  I have
heard of a primer called "The Compleat Cladist", written by Vicky Funk and
others, but I haven't seen it myself.  If you are interested, I can dig up
a couple of references in the primary literature that I think might be
accessible to undergrads (one that comes to mind is a book chapter by
Donoghue and Doyle about whether to analyze morpholgical data separately
from molecular data or together).

Good luck!

Judy Stone

==============================================================================
>I am teaching an introductory class in plant diversity and systematics to
>junior and senior undergraduates here at Grinnell College. At the beginning
>of the semester, I asked them to subscribe to TAXACOM to get a sense of the
>ideas workers in systematics are concerned about today.
>
>The thread was pretty dull for them, dealing mostly with priorities of
>publication and nomenclatural rules for which they have little background;
>so they sent a message to the list, but directed to the plant systematists,
>asking their opinion on what they regarded as the most significant,
>interesting, and important problems in plant systematics today.
>
>Surprisingly, to date, no replies have been forthcoming. So, on behalf of
>my class, I am asking the same question of the plant education discussion
>group. I will forward your responses to the class. (I was hoping that some
>of the ideas could serve as a basis for future class discussions). Thank
>you for your help.--Lenore Durkee
>
>Lenore Durkee                   durkeel at ac.grin.edu
>
>Department of Biology           515-269-3035 (office)
>Grinnell College                515-269-3027 (laboratory)
>
>P.O. 805                        515-269-4285 (FAX)
>Grinnell, Iowa 50112

------------------------------------------------------------------------
Judy L.Stone, Ph.D.               phone: (919) 660-7432
Dept. of Zoology                  fax:  (919) 684-6168
Box 90325
Duke University                   jstone at acpub.duke.edu
Durham, NC 27708-0325





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