Should I send a research recommendation letter to teaching postdoc position? I am a math PhD student, graduating this semester. I found a teaching postdoc that I would really like to apply for but I am confused by the ad. 
They ask for a teaching statement but no research statement. The duties include teaching two to three classes per semester and some course development/improvement. 

They ask for two recommendation letters, "at least one of which addresses your teaching." 
I have two teaching recommendation letters that I am pretty confident in.
But would it be concerning if I don't have a recommendation letter from my advisor? I just don't see the benefit in sending a research letter for a position that doesn't involve research, but I don't know how these things are judged. 

Any advice is appreciated!
It sounds like you are pretty dialed in.  My advice is to include the advisor letter.  For one thing they are explicitly open to some of the letters being non teaching.  And you have the teaching boxes checked.

Also, it still hopefully shows you in a good light: smart student, conscientious, etc.  If you could get your advisor to make some comments about any coaching, mentoring (or even personality suited to it) that would be a positive.  But even a straight research letter would still be fine.  Probably most of the committee did a research based Ph.D. so they know the world you come from even if the school is not an R1.  

I would not skip the advisor.  That will look bad.  (If it is OK to send 3 letters that would be ideal...but I don't know the protocol.)