Molecular vs. morphological types

Harvey E. Ballard, Jr. hballard at STUDENTS.WISC.EDU
Sat Nov 9 10:46:12 CST 1996


I fully accept the recent insights that we have gained from molecular data
regarding the dynamic nature of the taxonomic species many of us
systematists work with in monographic and floristic research.  I also
embrace the ideas that many species (not just allopolyploids) are para- and
even polyphyletic in evolutionary origin, that "progenitor" species by
their very nature will typically be paraphyletic in a cladistic sense; and
that cryptic species certainly exist in many groups.  The latter phenomenon
has long been known by zoologists and entomologists based on reproductive
and related behaviors, and both animal and plant cytogeneticists have been
documenting cytotypes (which some push to recognize as distinct species
despite frequent lack of morphological distinctions) for many decades.

I vehemently disagree with the concept of a molecular or cytogenetic or any
other type, however, divorced from a physical, morphological type specimen
for the simple reason that a single step removed from the specimen that
forms the basis of a name leads to innumerable potential problems of
interpretation.  I've encountered more than a few cases where morphological
holotypes were "lost" or misnamed by specialists, where isotypes were
confused or turned out to be mixed collections, etc.  And this where one
could go directly to a physical manifestation that "carries" the name of an
organism.  A preparation of any sort, anatomical, cytological,
biochemical--whatever--is one step removed from the tangible type material
and therefore has even more chance for nomenclatural mistakes or mixups or
switches or misinterpretations.  Basing a name on a preparation in the
absence of any morphological type specimen carries tremendous risk, in my
opinion.  I simply don't fully trust in ANY name, even fully in the
protologue or description of a name, in the absence of a physical
(morphological) type specimen, and that ideally a bona fide holotype
specimen.  I've encountered too many errors even with type material to
behave otherwise.  I've also been the victim of an occasional silly
misidentification of voucher material for a DNA extraction that I performed
(once of my own hasty identification and once, of another's) and also the
victim of a "bag-and-label" switch in which the voucher was correct but the
(then unrecognizable) material was of another species.  I realized the
problem when the ITS data placed the mixed-up material of both species in
anomalous positions in the phylogeny based on chromosome numbers and other
data.

While many of us systematists strive to accomodate evolutionary diversity
in a nomenclatural system, in whatever approach we might take, I agree with
Joe that an important factor in the recognition of taxa, in my own
research, must also be practicality: is it humanly possible to distinguish
a taxon without special aid beyond a dissecting microscope?  I remain
adamant against providing full species status to taxa that I cannot
recognize by some physical manifestation.  I do agree, however, in
characterizing a particular species with whatever data are available, so
that the whole "evolutionary" organism and its life history may be
appreciated, even if pragmatic taxonomic concerns important to the vast
majority of other biologists who must deal with the creature in the field
or herbarium cannot directly use the information.

My take: I trust no name that is unattached to a morphological type that I
can examine for myself and verify or reevaluate.  I accept the diverse
evolutionary history of many taxa, particularly of species, and applaud all
efforts to elaborate on the broader picture of species relationships and
species formation, but different "biotypes" must be attached to a
morphological type, whether or not someone decides to name them.  Depending
on the complex and how successfully one might be able to delimit a
"biotype" with features other than morphological ones, I might or might not
be willing to admit additional taxa at the species level or below it in
monographic or floristic treatments because of an overriding pragmatic
concern for the needs of biologists, naturalists and other "lay"
taxonomists that may be unable to utilize these taxonomic segregates
effectively.

********
Harvey E. Ballard, Jr.
Postdoctoral Researcher, USDA, Agricultural Research Service
Horticulture Department, University of Wisconsin
1575 Linden Drive, Madison WI 53706
phone: (608) 262-0159
and
Honorary Fellow, University of Wisconsin Herbarium
Botany Department, UW
132 Birge, 430 Lincoln Drive, Madison WI 53706
phone (608) 262-2792




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