Status of plant systematics
Thomas G. Lammers
lammers at FMPPR.FMNH.ORG
Thu Aug 28 10:50:48 CDT 1997
At 11:07 AM 08-28-97 -0300, Doug Yanega wrote:
>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.
The botanical Code (and DON'T get me started on bionomenclature; but do read
Dick Brummitt's essay in the same issue of Systematic Botany [22: 182-186])
recently added a provision for "epitypes" -- supplementary material that can
be designated to clarify the identity of a taxon if its type is equivocal.
I presume this would allow a given genotype (or chromosome number or
whatever) to be specified as that of the nomenclatural type.
> 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! ;-)
I think that in the botanical community at least, common sense would
prevail. Species concepts are much easier to modify than classifications
> 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
It will basically require several assumptions to be made, e.g., that
plants that share multiple characteristics can be assumed to have the same
or very similar gene sequences.
> 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
I would say "try to".
> 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?
By my definition, the best are. If they are not, then they are not
top-drawer, in my book. We musn't lose sight of WHY we do all this
sequencing, count all these chromosomes, measure all these length/width
ratios. These things are of absolutely no value in themselves. No
systematist really CARES about the sequence of this gene or that; a sequence
of A's, T's, C's, and G's is as exciting as reading a phone book (lots of
characters but no plot). There are no lists of all land plants with 15
chromosomes, no lists of angiosperms with ovate leaves, no lists of flowers
with pantoporate pollen; who cares? Those things are of no interest per se.
They are merely fuel and fodder for our primary mission. These data are
ONLY of value for what they tell us about how to divide up and organize the
biotic diversity we see around us, and about where it has all come from.
And THAT is only of lasting value to science and society if we codify our
conclusions in the form of a formal classification. From my perspective,
any activity that doesn't ultimately enhance the classification of the
world's biota is not part of our discipline, it is something else:
evolutionary biology, molecular biology, ecology, whatever. All valuable
fields, all contributing data useful to systematics, and in turn served by
systematics. But they are NOT systematics.
> 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.
As I am, obviously. We have an obligation to provide science and society
with useful classifications and names for the world's biotic diversity.
Anything that detracts from that mission needs careful examination. I
suspected fields other than botany were experiencing similar problems, but
to minimize fallout, I try to stick to what I know best when I stick my neck
out. (Interestingly, I've received three times as many positive comments
privately than on the list -- guess others didn't want to seem like a
"fossilized curmudgeon" either).
Aside from practical concerns, I reiterate my original conceptual concern:
that it is illogical for a discipline that has diversity as its centerpiece
to devolve to a condition where all its practioners MUST adopt just one of
many possible approaches in order to survive. Is there ONE graduate student
out there who was NOT told "You'd better include molecular techniques or
you'll never get a job." Even those of us who do not employ such
techniques reluctantly tell our students that. Is there a systematics
position at a major university in this country that has NOT been filled by a
molecular systematist in the last five years? Has there been one
departmental search committee that has said, "By God, what we need around
here is a good monographer?" Answer these questions honestly, and you'll
see why some of us are concerned. We are putting all our eggs in one basket,
and I fear that will cause us problems someday.
Thomas G. Lammers
Classification, Nomenclature, Phylogeny and Biogeography
of the Campanulaceae, s. lat.
Department of Botany
Field Museum of Natural History
Roosevelt Road at Lake Shore Drive
Chicago, Illinois 60605-2496 USA
e-mail: lammers at fmppr.fmnh.org
voice mail: 312-922-9410 ext. 317
"One must remain aware of the
real-world consequences of his philosophies."
-- Phil Mole
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