Subject: Evolution of phenotypic plasticity

What is the evolutionary role of phenotypic plasticity?

Is it purely genetic in origin or does it represent 

environmental variance as well as additive genetic variance?

Is it a result of microevolution (i.e. selection) or is it

macroevolutionary in nature?  Finally, does phenotypic 

plasticity act as a sort of buffer to evolution by providing

non-evolutionary responses to pressures which might otherwise

create a scenario of gene selection (i.e. evolution by

selection).    

Re: Evolution of phenotypic plasticity