Subspecies, ecotypes and conservation of biodiversity

John Shuey Shueyi at AOL.COM
Thu Jun 12 19:33:20 CDT 1997


<Some weeks ago I posted a question to this list headed "the value (or not)
<of subspecies". I asked for replies off list for which I was (justifiably)
<chastened by certain other list members. Their point being that this is a
<'hot topic' deserving of wider discussion. The responses I received
<represented both ends of a full spectrum of opinion and everything in
<between! For these reasons I would like to throw open the debate to the
list.



<My interest originates from a conservation viewpoint - to maintain
<biodiversity and the ecological and evolutionary processes supported by it.
<Patently, new species come in to being at the population level and must have
<transient 'subspecies' stages which can be identified (Note that I refer not
<only to the formal taxonomic rank of subspecies but to any subspecific
<structuring). Local species assemblages and regional variants then produce
<unique communities. So is it valid to only conserve 'representative samples'
<of species (the conservation equivalent of taxonomic 'types') when such
<variation exists?

First, note that I picked this post up on two lists, consbiol and taxacom,
which in that order, reflect my primary interests, both professional and
personal, as well as the prioritization of my biases.

Unstated or not (depending on the target audience), most applied conservation
biologists are trying to conserve evolutionary potential of all species, and
are willing to use any tool that is available.  The existence and recognition
of valid differentiates, be they formally named or not, is one of those tools
that may help conserve genetic diversity within a species.  A named entity,
be it a plant variety or a subspecies in the traditional sense, draws
attention to a taxon which it might not otherwise receive.  Thus, the named
entity can more easily become a conservation target separate from other
con-specific differentiates - conserving a variety of differentiates at the
species level is one way to help insure that species-level genetic
variability is conserved.  The obvious example is when a subspecies becomes
federally listed as endangered or threatened in the USA - suddenly it gets
some attention.  At a less recognized level of activity, State Heritage
Programs use these taxa at the state level for conservation planning
purposes.  Thus in Indiana, we protect several sites in part because of the
presence of  French's shooting star, _Dodecatheon media_ var. Frenchii, a
variety that is primarily found on sandstone cliff faces.

But recognizing and potentially listing every differentiate of every species
is never going to happen.  The pool of taxonomists available is not adequate,
and current trends of taxonomic interests are generally biased toward other
taxonomic levels.  Even if every differentiate were named, and we actually
knew which differentiates needed listing, listing thousands of varieties and
subspecies would be a political disaster.  As it stands today, about 33% of
vascular plant taxa in the US are considered to be at risk.  Could you
imagine the back-lash that would ensue if suddenly the number of listed taxa
increased by an order of magnitude.  We would likely lose our currently
tenuous grip on the Endangered Species Act itself.

The other tool currently used to protect evolutionary potential is common
sense.  If we recognize that our ultimate goal is to conserve evolutionary
potential in all taxa, and that evolutionary potential varies in response to
environmental gradients, then the conservation goal should be to capture
viable samples of everything across these gradients.  We could plan on a
species by species basis, (the so-called fine filter approach in Nature
Conservancy lingo), but we all realize that this is an impossible task.
 Species-level planning is appropriate for some critically imperiled taxa,
but for the vast majority, we would spend decades planning and likely have
few resources remaining for implementation.  The vast majority of terrestrial
species in the US (and likely elsewhere) can be conserved using a "course
filter" approach -- identify terrestrial community types, eg, mesic upland
tillplain forest, and make sure that some minimum number of appropriately
scaled sites (implied here is some assurance of viability of both plant and
animal communities) across the geographic distribution of the community.  By
planning by community type to ensure geographic representation, we can
capture and protect evolutionary potential in almost all species.  Of course
the extremely rare taxon, and large, area sensitive mammals may fall through
the cracks in some areas - species specific planning is probably the answer
for these.

Obviously, for this "coarse filter" to work, we need a "stable taxonomy" of
community types.  This is in fact in the final stages of development for the
entire US, and there are likely to be a couple thousand named terrestrial
community types when all the dust settles.  Conservation planning for this
many targets will be a difficult task, but is already underway.  And it will
certainly be an easier task than planning for all species or population
differentiates.  Aquatic communities are less well known, but a frame-work
for aquatic community classification is also being developed for conservation
purposes.  And caves? - who knows but in Indiana we are at least trying to
delimit the clusters of narrowly endemic taxa as our best guide to protecting
this oft-forgotten class of communities.

In summary, applied conservation uses the tools that work best for the
problem at hand.  Formally recognizing taxa at any level may at times be the
best tool, and personally, I love subtle differentiates and have probably
named a couple of things that others hate.  Differentiates are informative,
especially congruent clusters of widely diverse higher taxa.  But the real
answer for effective conservation is an approach which captures biodiversity
at all of its organizational levels. A well-planned biological
community-based approach - tuned with fine filters as needed - seems most
likely to produce success in the short time we have available.


John Shuey
Director of Science and Conservation Biology
Indiana Office of The Nature Conservancy




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