[R-sig-ME] anova

[Cougar]

I wonder if it is possible to nest a generalized least squares model within
an lmer model for the purpose of testing the hypothesis that sigma.sq_beta_0
= 0.

Example: R 2.5.0, WinXP

>library(lme4)
>data(sleepstudy)
>library(nlme)
>m0 <- gls(Reaction ~ Days, sleepstudy)
>m1 <- lmer(Reaction ~ Days + (Days|Subject), sleepstudy)
>anova(m0,m1)

I do not get any result from the anova.  I assume it is because the model
objects are of different classes.  Is that correct?

Respectfully,

Frank Lawrence