This study structures the ecosystem literature by using a bibliometrical approach in analysing theoretical roots of ecosystem studies. Several disciplines, such as innovation, management and software studies have established own streams in the ecosystem research. This paper reports the results of analysing 601 articles from the Thomson Reuters Web of Science database, and identifies ten separate research communities which have established their own thematic ecosystem disciplines. We show that five sub-communities have emerged inside the field of software ecosystems. The software ecosystem literature draws its theoretical background from (1) technical, (2) research methodology, (3) business, (4) management, and (5) strategy oriented disciplines. The results pave the way for future research by illustrating the existing and missing links and directions in the field of the software ecosystem.