Dear Liz et al.,

The distribution of species collected at a single station by their
frequency, given a good measure of biodiversity, always has a bunch of
"stragglers" (only one or two examples of certain species).  A typical
example (and one in which human selective factors had been minimized) is
Charlotte Lloyd's report discussed recently in this forum
<http://home.sprynet.com/~wfrank/remarkab.htm>.  Look at all the species
preceded by a "1"!

Corollary to this pattern, which I have witnessed in fossil and Recent
land, marine and aquatic field collections over 50 years of noodling for
shells and their contents, is the fact that there WILL be additional taxa
(given a diverse and robust regional fauna) on a revisit to the same
collecting site.

The numbers-crunchers can model this frequency distribution into some kind
of chi-square or asymptotic transmogrification, but the "straggler" concept
is good enough for me.  I think this experience is a paraphrase of Andy R's
hypothetical melange of field trips to the Cretaceous pit and Liz's posting
below.

Now to tackle that recommended reading of high specific gravity prose (vide
infra)!

Harry


At 06:26 PM 6/21/00 +0100, you wrote:
>Dear all,
>
>As Andrew points out, the expectation is a curve which rises sharply
>and then tails off. Since there is rarely enough time to exhaustively
>collect and identify every specimen it is not surprising that
>ecologists have devised various ways of estimating species diversity.
>If anyone is interested, the friendliest book on the subject I know
>is:
>
>Magurran, A.E. (1988) Ecological Diversity and its Measurement.
>Chapman & Hall.
>
>From the replies coming in, it looks as if conch-l collectively has
>some interesting data on the subject.
>Liz
Harry G. Lee
Suite 500
1801 Barrs St.
Jacksonville, FL 32204
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Visit the Jacksonville Shell Club Home Page at:
http://home.sprynet.com/~wfrank/jacksonv.htm

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