Re: NANFA-L-- Diversity Indicies

Bruce Stallsmith (fundulus at
Thu, 29 Sep 2005 16:35:37 -0400

Martin, you actually understand what's going on without realizing it. There
are different concepts of evenness, vs. species richness, vs. diversity.
They're not all the same and if you're a researcher dealing with sample data
sets you have to be clear in your mind what you're really asking; there is
no one good statistical tool or concept (even though I keep praising Hill
and Hurlbert...). This is why the question of statistical testing and
interpretation is always an ongoing debate when considering biodiversity,
diversity, whatever.

--Bruce Stallsmith
now I have to go give two tests along the Tennessee...
Huntsville, AL, US of A

>From: Irate Mormon <archimedes at>
>Reply-To: nanfa-l at
>To: "nanfa-l at" <nanfa-l at>
>Subject: Re: NANFA-L-- Diversity Indicies
>Date: Thu, 29 Sep 2005 16:27:46 -0400
>Quoting Bruce Stallsmith <fundulus at>:
> > The trick to, and differences between, various types of diversity
>indices is
> > to measure how even the species distributions are. If you have 100 fish
> > your sample, and these represent 10 different species, how do you
> > it if you have 10 individuals of each species in your sample, or maybe
> > have 91 individuals of one species and one individual of each of the
>other 9
> > species? This gets into ideas of evenness, and what are truly common
> > species, and how sensitive your statistical measure is to the presence
> > species represented by only one individual in a much larger sample.
>Does evenness matter if you are measuring diversity (whatever that is)? I
>see how you could build an index for species richness, or species evenness,
>when you try to combine both, what exactly do you get? I guess if you
>2000 fathead minnows and one stickleback out of a baitshop tank, that
>sample is
>somehow less diverse than if you collect 1000 fatheads and 1001
>BUT if you give more weight to the fatheads in the first example, because
>that one stickleback really wasn't supposed to be in there, then you are
>interpreting the data and extrapolating from it, rather than merely
>(quantifying) it. A fine point perhaps, but what you are actually doing is
>building prejudice into the index. And maybe that's exactly what you want
>do? I guess it would help if I knew what diversity was.
>Now, your point about having a number to give to bureaucrats, THAT I
> They can point at the number and say, "Hey, that meets our guidelines
>to section C, subparagraph IIa: 'Laws Governing Timelords'" without
>concerning themselves with what it means.
>"Mos' peoples is intell'gent" - Mudbone
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