This article explores the commitment of Quebec telecommunication businesses to an innovative ecosystem. Open innovation is the purpose of this commitment and it gives rise to co-opetition relationships between the ecosystem members. This study describes the emergence of co-opetition relationships in ecosystem and explains their evolution. The longitudinal methodology zeroes in on two ecosystems, namely one successful and the other in decline. We propose a three phases model to explain ecosystem evolution and a typology of players rationality as they evolve in an ecosystem.