[R-sig-ME] p-values in lme vs gamm

[Etienne Laliberté]

With gamm from the mgcv package, I'm struggling to understand the
difference between summary(mymodel$gam) and summary(mymodel$lme).

In particular, can someone enlighten me as to why some of the p-values
differ with the following two calls? Without smoothers, I thought gamm
would simply give the same results as lme().

library(mgcv)
data(oats)
lme.mod <- lme(Y ~ N + V, random = list(B = ~1 , V = ~1), data = oats,
method = "REML")
gamm.mod <- gamm(Y ~ N + V, random = list(B = ~1 , V = ~1), data = oats,
method = "REML")
summary(lme.mod)
summary(gamm.mod$gam)
# note different p-values for VMarvellous and VVictory

Thanks

Etienne