Thank's a lot for your help Ben.
I already posted my question on r-sig-mixed-models! However you already
answered what I needed to know.

2012/3/27 Ben Bolker <bbolker@gmail.com>

> Lívia Dorneles Audino <livia.audino <at> gmail.com> writes:
>
> >
> > I'm trying to make a glmm to identify the relationship between insect
> > species richness with fragment size, isolation and time (different
> years).
> > I already tried to analyse it using poisson distribution error, but I
> > always face with the following warning:
> > *glm.fit: fitted probabilities numerically 0 or 1 occurred *
> >
> > This is probably hapenning because my dataset has a lot of zeros. So,
> what
> > error distribution should I use?
> >
>
>   I know you haven't gotten a lot of help on r-sig-mixed-models (sorry),
> but it would probably be better to post this question there.  The answer
> is that this is a warning, not an error, so it indicates a need for
> caution but not necessarily that anything is wrong.  In this case,
> an internal call to glm.fit() has difficulty when it tries to fit
> a subset of that data that are all-zero or all-one.  It's quite possibly
> OK, provided that you've looked at your results, plotted predicted values,
> etc., and everything seems to make sense.
>
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>



-- 
*Lívia Dorneles Audino*
Doutoranda em Entomologia
Laboratório de Ecologia e Conservação de Invertebrados
Universidade Federal de Lavras

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