Natural Boundaries

John Grehan jrg13 at PSU.EDU
Tue Apr 27 03:29:41 CDT 1999

>John Grehan talks about "natural" boundaries.  However I think this idea
>may tend to over-compatmentalize things.  When boundaries are drawn on a
>map, or any other surface for that matter, be they political, ecological,
>or whatever, is there anything natural about them, or are they all artifical?

In my opinion they are all artificial. This opinion appears to be shared by
others, but with the view that such areas nevertheless have untility or are
"useful". My contention is that however useful in whatever political,
or philosophical context, such areas do not constitute units of biogeographic
analysis because they do not represent any kind of homology concerning
the origins of distribution patterns.

I would go further with Colin Kaneen's observation to day that boundaries
around things in nature may not be stable and can be very hazy to assert that
such boundaries have no real existence - which Colin also hints at by
noting that nature does not obey a line just because we have drawn it.

As for the question of whether there is any way to show a truly natural
boundary, from my perspective the answer is yet, but the boundary is not
drawn as a boundary external to the organism. In panbiogeography for
example, the intersection of two or more tracks constitutes a node, and a
node is a biogeographic boundary. While the node may be graphically displayed,
it has no particualar geographic boundary. Its reference is the distribution of
organisms concerned. At least that's how I look at this concept.

Regarding the conventional notion of boundary, there are some comments in the
panbiogeography book on its influence on the interpretation of distributions.
Once drawn the boundaries were, of course,
"crossed" by those distributions that did not obey them. Such distributions
(or the
organisms responsible) are widely seen as transgressors, with taxa begining
in one
region and invading another. Another view expressed by some French authors was
that such taxa represented "especes de liason" which suggested there were a
more fundamental
relationship than the boundary itself.

John Grehan

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