If you are trying to synthesize results from different communities, then
having some undefined really messes things up. Better to have a poor
definition than run to "undefined". An alternative is to weight the measure
by the number of species so that with zero species you have a real zero.
It sounds to me like UA or US (which is it?) may have too many philosophers
on staff!
Bill Silvert
----- Original Message -----
From: "Eric Lamb" <el...@ualberta.ca>
To: <ECOLOG-L@LISTSERV.UMD.EDU>
Sent: Friday, July 17, 2009 12:14 PM
Subject: Re: [ECOLOG-L] Shannon-Wiener Div Index Question - dealing with
zero species per plot??
The consensus seems to be that diversity should be zero, but we should
consider the larger question before the mechanics of calculating a
particular index.
I recently had to deal with a similar question: what is the evenness of a
community with zero species?. The consensus among those I discussed this
issue with was that evenness (and hence diversity) should be undefined
when
there are no species. The reason is that diversity or evenness is a
property
of a community, not a patch of ground or a pot. If there are no species
then
there is no community, and thus we cannot define evenness.
Cheers, Eric
--
Eric Lamb
Assistant Professor, Plant Ecology and Biostatistics
Dept. of Plant Sciences, University of Saskatchewan
http://homepage.usask.ca/egl388/index.html
4D68 Agriculture Building
306-966-1799
eric.l...@usask.ca
