[R-sig-eco] a mixed-effects model?

[Lara R. Appleby 04]

I manipulated food availability ("treatment"=none, low, or high) of individual  
queens of two ant species ("species" = 1 for Pogonomyrmex barbatus or 2 for Pogonomyrmex  
occidentalis). I counted the offspring produced in the first clutch of each queen  
(clutchsize). I also measured the initial mass of each queen (qinit) because it  
might affect clutchsize. Queen initial mass differs alot between the species.  


I want to know the extent to which food availability and species independently  
affect clutch size, taking into account the likely affect of initial queen mass  
and the extent to which there is an interaction effect of food availability and  
species on clutch size.

Since food availability and species are fixed effects, queen initial mass is a  
random effect, and the explanatory variable is clutch size, my model is

lmer(clutchsize~treatment*species+(1 | qinit))

Is this how you would approach these data?

Lara R. Appleby
Ph.D. Candidate
University of Houston