[R] does lme repeated measures require sphericity?

[John Christie]

I haven't been able to find an answer on this that's direct, only  
implied.  In several places I have read that when people asked for  
sphericity tests they were guided toward lme or mlm models.  But,  
there is no direct indication that the lme method is not subject to  
the sphericity assumption.  In fact, it seems like it should be.  Its  
just a linear model that handles random and fixed effects.  I imagine  
most other parametric assumptions hold true.