While digital transformations are taking place, we still have limited understanding as to how ecosystems and supply chains differ from a theoretical standpoint and how they relate practically. We study the evolution of the concept of ecosystems through a systematic review of the literature to describe how the two concepts relate throughout this evolution. We use cases to investigate how ecosystems and supply chains relate practically. We show that non-contractual governance in a supply chain facilitates investment in specific assets by a few key suppliers, while non-contractual governance in an ecosystem facilitates the creation of collective shared assets by many ecosystem participants. We also show that practically supply chains and ecosystems can either compete or complement each other and we present some of the conditions for the emergence of such relations.