Re: NANFA-L-- Diversity Indicies

Irate Mormon (archimedes at
Thu, 29 Sep 2005 15:30:59 -0400

Quoting "dlmcneely at" <dlmcneely at>:

> At the risk of irritating those who want to get on to other things:
> I think Todd wants to include something like overall rarity (of the
> species wherever it might occur), or some sort of "value" for
> particular species (a common carp is worth considerably less in most
> systems than, say, a golden redhorse), in order to have a score that
> reflects some kind of "condition" for the system sampled. Rare species
> being common in a place might indicate its condition, or intolerant
> species being common might also.

I'm with you so far. I also note your use of the term "condition" in the
loosest sense. It seems to me that the way we define certain habitat as somehow
being of superior "quality" to another (at least on this list) is pretty
meaningless. From the fish's point of view, whatever that fish likes can be
considered highest quality, even if that's the only fish that can live there.

It sounds like comparisons of this nebulous "condition" between systems must
also be ambiguous, if the same animal is weighted differently in different
systems. Therefore (and I don't wish to seem argumentative or contrary), how is
all this useful, other than saying we can put a number on "something" that we
want to quantify? I'm not trying to pick a fight, I just don't get it...?!
Like I said, I was never exposed to this stuff.

I am also intrigued by the difference between the concepts of diversity and
richness. I gather that richness simply means number of species, but what is
diversity? Would that be measured by lineage, habitat preference, food
preference, number of bumps on the tongue, or ... what? And is this a
_meaningful_ distinction (to wit, "A difference which MAKES no difference IS no
difference.") ?

Maybe those interested could reply offline, so as to streamline the list?


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