1) Caller 
• (n.) One who convenes or meets with others. • (n.) One who calls an assembly together or convenes a meeting; hence, the chairman of a committee or other organized body.
Con·ven'er noun 1. One who convenes or meets with others. [ Obsolete] 2. One who calls an assembly together or convenes a meeting; hence, the chairman of a committee or other organized body. [ Scot.]
[n] - (British) the member of a group whose duty it is to convene meetings
noun the member of a group whose duty it is to convene meetings