Liam Revell wrote:
> > Poaching Intensity = beta0 + beta1*Body Size + e
>
> I think it depends on how the residual error in the model is
> distributed (esp. correlated) among species. It seems possible to
> invent hypothetical scenarios (as I did in my previous email) about
> how the residual error in poaching intensity given body size could
> be phylogenetically autocorrelated, but this is fundamentally an
> empirical question. If the residual error of poaching intensity
> given body size is phylogenetically correlated and we ignore this
> then we risk overestimating the predictive value of our model.
>
> In addition, the residual error is likely/guaranteed to be non-
> Brownian if the response variable is binary (e.g., extant v.
> extinct). For these type of data the tree should not be ignored,
> but simple GLS regression is probably not appropriate. One option
> might be the phylogenetic logistic regression of Ives & Garland
> (2009), but I'm not too familiar with this method.
The real problem would come if the characters evolved to respond to
the poaching intensity, and that evolution was inherited along the
tree. Then our uncertainty about the poaching intensity in the past
would be a big problem.
But if poaching is only a present-day phenomenon, it would
(presumably) respond to only today's characters, and they would not
yet have responded to it, so there would be no problem.
But I do think it is a Big Mistake (and apparently a frequent one),
when people measure the residual of a character regressed on
environmental variables,
then casually assume that it is undergoing Brownian Motion, when the
environmental variables may have been different in the past. That's
probably not an issue here.
Joe
----
Joe Felsenstein j...@gs.washington.edu
Dept of Genome Sciences and Dept of Biology, Univ. of Washington,
Box 5065, Seattle Wa 98195-5065
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