How do you maintain alpha status in group conversations?

I'm passable at smaller conversations, but once they get to 4+ people I find it hard to keep the focus of the girls. I can be decently witty and such, but other guys seem to have more charisma. I believe I carry myself well, and I don't look that bad.

The problem: other guys are seen to be more leaders in groups, and thus more desirable. How do I solve that?