Subject: Ehrlich experiment: the real reference!

From: [email-masked] (Thomas H. Slone)
Date: 25 Mar 1996 20:35:26 GMT

In article <[email-masked]> you write:
>        In  the paper 'Checkerspot Butterflies: A Historical Perspective',
>by Ehrlich, White, Singer, McKechnie, and Gilbert (1975), Science 188:221-
>228, is the following paragraph:

>        Reference (12) reads:"P. R. Ehrlich, unpublished data."

I believe the real reference is:
Harrison, S; Quinn, J F; Baughman, J F; Murphy, D D; Ehrlich, P R
Estimating the effects of scientific study on two butterfly populations.
American Naturalist 137(2):227-243(1991).

Abstract:
Two populations of the butterfly Euphydryas editha were repeatedly
sampled for scientific study over a period of 22 yr. Bootstrap
simulation models indicate that the effects of this perturbation on
expected population sizes are not statistically detectable at any time
during or after the period of sampling because of the large variance of
yearly rates of population growth. However, the models indicate that
sampling increased the chances of extinction for the two populations.
The estimated amount of this increase depends on whether the
populations are assumed to be density-independent or weakly
density-dependent.
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