After reading this posting and several replies I am getting more and more
confused. Of course both n=0 and n=1 correspond to zero diversity. What is
the issue?
More fundamentally, what is the point of all of this? In the rest of her
posting (which I have omitted) she describes a project for which she wants
an index, but I think that the output of an ecological study should be a
statement about the ecosystem, To say that bees prefer substrate X to
substrate Y is informative, but to simply report the value of some
arbitrarily chosen diversity index is not, at least not so far as I can
tell.
Perhaps if she has some biologically meaningful hypotheses to test it would
be easier to identify some index that can be used to distinguish between
them. She writes "I am studying substrate preferences of ground nesting
bees" but it isn't clear how any diversity index fits into the analysis.
Bill Silvert
----- Original Message -----
From: "Maria Van Dyke" <mt...@virginia.edu>
To: <ECOLOG-L@LISTSERV.UMD.EDU>
Sent: Thursday, July 16, 2009 6:39 PM
Subject: [ECOLOG-L] Shannon-Wiener Div Index Question - dealing with zero
species per plot??
I have a question about utility of the Shannon-Wiener diversity index in
regards to sampling units that have no species in them at a given sampling
time. Normally this would get a value of zero, however with Shannon-Wiener
a
sampling unit that has only one individual of one species would also earn
the value of zero when input into the formula -∑(1*ln1)
= -&#8721;(1*0) = 0;
therefore there becomes an issue of two different species scenarios having
the same values (0 for no species individuals and 0 for 1 ind of one
species).
