Thank's for your help Peter!
This post is really very informative. It helped a lot!

2012/3/27 Peter Ehlers <ehlers@ucalgary.ca>

> On 2012-03-27 15:11, Ben Bolker wrote:
>
>> 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.
>>
>>
> Livia:
>  You might also find this quite extensive recent post from Ted Harding
> informative:
>
>  https://stat.ethz.ch/**pipermail/r-help/2012-March/**307352.html<https://stat.ethz.ch/pipermail/r-help/2012-March/307352.html>
>
> Peter Ehlers
>
>
> ______________________________**________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/**listinfo/r-help<https://stat.ethz.ch/mailman/listinfo/r-help>
> PLEASE do read the posting guide http://www.R-project.org/**
> posting-guide.html <http://www.R-project.org/posting-guide.html>
> and provide commented, minimal, self-contained, reproducible code.
>



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

	[[alternative HTML version deleted]]

