You've received great info from aeh. I'll just add that an individual may be both gifted and on the Autism Spectrum.

If you're looking for links to more resources here are a few:
1) Article on Davidson Database
2) CDC summary of diagnostic criteria for ASD
3) DSM-5 factsheet on ASD
4) SENG article on misdiagnosis and dual diagnoses of gifted children
5) 2e newsletter
6) Hoagies Gifted Education Page