Rare species

[Dennis Paulson]

Eric Metzler wrote:

>Vulnerable, as defined here with rates of decline, is also the
>equivalent of "threatened" which is a legal definition, not to be
>bandied about when one is talking about infrequently encountered species
>rather than species which need governmental protection.  In my opinion,
>the definition at this WWW page further confuses the issue by combining
>two completely different situations - (1) the decline of species with
>(2) frequency - in a single definition.  This situation illustrates my
>frustration that "rare" can easily be translated to "threatened," thus
>eliciting protection when none is needed.
>
>Until a better definition is provided, the word "rare" is unfriendly.  A
>researcher can be prohibited from studying a subject by simply defining
>the subject as "rare."  It happens.

I agree that we may have to distinguish *rarity* for its interest to
biology from *rarity* for its importance to conservation; they aren't
necessarily the same. At one time in Washington, all the birds that had
been seen a few times in the state (such as an Ivory Gull wandering down
from the Bering Sea) were considered "species of special concern" by the
agency "in charge" of Washington wildlife. Fortunately, this was ridiculed
sufficiently so that some definitions of rarity were quickly revised, but
the potential problem is as Eric mentioned.

I have resisted calling attention (as possibly vulnerable) to a dragonfly
species that I described from a single short stretch of river in
Washington, as I concluded that as a consequence of this it was far more
likely the species would be "protected" so I could no longer collect
specimens of it than that the entire rivershed would be "protected" so no
harm could come to the species. Ohio, Eric's home state, has been
wonderfully perceptive in allowing dragonflies (and other insects?) to be
listed as of special concern, yet not banning their collection by
researchers, but not all state and federal agencies are so sympathetic to
science.

On another matter, I think the presence of two quite different kinds of
rarity is indeed significant to conservation. Thomas Lammers wrote that
populations of the "lots of individuals in one or a few tiny areas" type
are more at risk than those of the "few individuals scattered over a large
area" type, and I can see his point. However, the former types are much
more easily protected than the latter, so I don't agree that the latter are
necessarily more secure. Because they are so scarce, they can disappear
literally before we know it, whereas the concentrated, local populations
can be more effectively monitored. And the sex-ratio and mate-finding
problems are ever so much more critical for the sparse populations, even
though they are presumably better off from the standpoint of outbreeding.

Dennis Paulson, Director                           phone 253-756-3798
Slater Museum of Natural History                 fax 253-756-3352
University of Puget Sound                       e-mail dpaulson at ups.edu
Tacoma, WA 98416
http://www.ups.edu/biology/museum/museum.html