Teams comprised of both humans and robots are increasingly becoming a reality. A key barrier to enabling teams fluently working together is that leadership roles of humans and robots are often determined a priori. In successful human-human teams, we find that leadership is an emergent behavior where team members can adaptively take, give up, or share leadership based on changing tasks or environments. To create human-robot teams capable of long-term interactions in dynamically changing environments, they need to be able to fluidly adapt leader and follower roles.