[R] Why does dredge() rank models differently for lmer() and MCMCglmm()?

[Ben Bolker]

Corina <itsme <at> CorinaLogan.com> writes:

> 
> Hello,
> I am running my full model (fm) through lmer() and MCMCglmm() using the
> default settings:
> 
> model.lmer <- lmer(fm)
> model.MCMCglmm <- MCMCglmm(fm)
> 

  [snip]

> However, when I run the models through dredge():
> 
> dredge(model.lmer)
> dredge(model.MCMCglmm)
 
> It ranks the models very differently for lmer() and MCMCglmm() in
> the model selection tables, even though I used the default settings
> for dredge() as well (ranked by AICc). I would assume the difference
> is because lmer() uses REML and MCMCglmm() uses Bayes Rule, however
> if this is the case then why weren’t the summary outputs different
> as well?
 
  [snip]

   This question *might* be better on r-sig-mixed-models at r-project.org ...
You shouldn't be comparing models with fixed effects that are fitted
with REML -- try  refitting with REML=FALSE.  The model comparison
functions in the lme4 package (e.g. anova()) try to stop you from 
making this mistake, but I'm not sure the MuMIn::dredge does.