Systems-of-Systems (SoS) have become increasingly complex and frequently used in highly distributed, dynamic, and even open environments. SoS refer to evolving software systems, where constituent systems (themselves systems in their own right) work cooperatively to fulfill specific, complex missions, facing software engineering researchers and practitioners with substantial challenges. 
In parallel, Software Ecosystem (SECO) has also become an important research topic in software engineering, addressing social issues along with technical aspects of software development. SoS and SECO are closely related, also naturally distributed so as the distribution of development teams, along with the inherent difficulties of coordination and communication. 
In this scenario, Distributed Software Development (DSD) deals with distributed resources to reduce cost and reach new IT markets. Inherent problems and challenges of software engineering are then amplified and become more critical when those three topics need to be analyzed together. 
This special edition of SESoS/WDES 2017 will provide researchers and practitioners with a forum to exchange ideas and experiences, analyze research and development issues, discuss promising solutions, and propose theoretical foundations for development and evolution of complex systems, inspiring visions for the future of software engineering for SoS, SECO, and DSD and paving the way for a more structured community effort.