Explaination of front wing design

[SlideWRX]

Since that part of the wing sits on the body, it probably has slightly different airflow, and wants a different profile to the wing for best use. I'll bet the serrations help without messing up airflow over the rest of the wing.

[ecomodded]

It sure looks like a vortex generator, being in front of the body, it would cause turbulence's that would pass over the upper body, attaching the air flow off the air dam.
Possible it could re leave some back pressure from the cars nose as well.