Status of plant systematics

Doug Yanega dyanega at MONO.ICB.UFMG.BR
Thu Aug 28 11:07:15 CDT 1997

Tom Lammers wrote:

>At 03:43 PM 08-27-97 -0700, Curtis Clark wrote:
>>I agree with much of what you say, and your reasoning about the previous
>>intractability of family-level questions makes good sense. (I might add to
>>that the observation that species-level problems are commonly proving
>>intractable with the current set of molecular tools.)
>Yes, that's true, though it seems only a matter of time before genes are
>found that will yield suitable data at this level.

There is a serious limitation here, however, that you don't mention - in
order for molecular tools to be truly useful to alpha taxonomy, we must be
able to apply these tools directly to our holotypes, and all the other
specimens of the taxa for which we cannot get new, fresh material for
analysis. If you can't sequence the holotype, or other ancient preserved
material, you can't easily blend classical alpha taxonomy and nomenclature
with sequencing. This is more of a problem, I think, for folks studying
arthropods than plants, as there may be more physical tissue in the average
plant holotype, as well as a larger proportion which can be destructuvely
sampled without seriously compromising the utility of the type for
morphological comparison. I suspect, of course, that eventually the
techniques may become refined enough to extract viable sequences from even
infinitessimal amounts of ancient, desiccated tissue.
        This would, however, raise (to me) an ugly spectre if it *does*
become practical; literal application of the phylogenetic species concept,
combined with sequencing, would - I would expect - lead to the vast
majority of plant and animal taxa each being "split" into an array of
morphologically identical but genetically different "species". After all,
most plants and animals are known from a small enough sample of material so
as to make it very difficult to distinguish consistent population-level
differences (the important criterion for the PSC) from variation. If all
one has is five specimens of a taxon, but all five are genetically
different from one another, and from different localities, then a molecular
taxonomist might well designate each one a species. Even if one should
accept the idea, this would also make it almost impossible for anyone to
identify any organism to species *without* sequencing it. If we thought we
had problems rectifying taxonomy with the BSC, just wait! ;-)
        Basically, all I'm trying to say is that while I fully agree that
molecular techniques have great potential to help us resolve higher-level
classification, I think there are some significant potential problems in
taking it down to the species level. I'm not sure I see how we can ever
satisfactorily integrate molecular systematics with alpha taxonomy unless
we completely rethink our concepts of how taxa are defined, in both theory
and practice.
        A final question for Tom and others on this thread: you state that
the best young plant systematists know how to integrate ALL the evidence in
their analyses, and this is reassuring for the future of systematics in
general - but are these promising young folks committed to doing *alpha*
systematics? Are they familiar with the nuances of nomenclature, type
designation, and the like? If not, then maybe the statements as to
"endangered" status need to be qualified as to which *type* of systematic
research is imperiled? It might not be a concern if we were satisfied that
we had defined and named every species on earth adequately already, but we
are a long way from that goal, and it's obviously going to be harder to
make progress if alpha taxonomy gets less and less support. Frankly, I'm
still more than a little worried, and not just for botany.


Doug Yanega    Depto. de Biologia Geral, Instituto de Ciencias Biologicas,
Univ. Fed. de Minas Gerais, Cx.P. 486, 30.161-970 Belo Horizonte, MG   BRAZIL
phone: 031-448-1223, fax: 031-44-5481  (from U.S., prefix 011-55)
  "There are some enterprises in which a careful disorderliness
        is the true method" - Herman Melville, Moby Dick, Chap. 82

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