On AIC and relative log-likelihood (which they call evidence ratio):
Symonds, M.R.E and Moussalli, A. (2011). A brief guide to model selection, multimodel inference and model averaging in behavioural ecology using Akaike's information criterion.Behavioral Ecology and Sociobiology, 65, 13–21. doi: 10.1007/s00265-010-1037-6
See Also
logLik; AIC; BIC
Examples
# see example in LMERConvenienceFunctions help page.