In the strategic management field, the ecosystem concept is increasing significance. This paper provides an overview of 90 previous studies on the ecosystem concept published in leading academic journals in strategic management field and clarifies the four major research streams. The first perspective is the industrial ecosystem perspective, which is based on the concept of industrial ecology. The second perspective is the business ecosystem perspective. This perspective is based on the theory of organizational boundaries. In the business ecosystem perspective, some influential scholars emphasize platform management, which represents the third perspective, the platform management perspective. The fourth perspective is the multi-actor network perspective, which contributes to the dynamic behavioral relationship analysis based on social network theory. This perspective expands the range of analysis to include various actors in addition to private companies. As a result of the review, this study presented the integrated map of the previous works. Furthermore, this paper proposed original ecosystem concept, definition, and scheme for designing or re-designing coherent ecosystem. The coherency is the core concept for the evolution and expansion of the ecosystem.