The development of a software system is now ever more frequently a part of a larger development effort, including multiple software systems that co-exist in the same environment: a software ecosystem. Though most studies of the evolution of software have focused on a single software system, there is much that we can learn from the analysis of a set of interrelated systems. Topic modeling techniques show promise for mining the data stored in software repositories to understand the evolution of a system. In my research, I seek to explore how topic modeling techniques can aid in understanding the evolution of a software ecosystem. The results of this research have the potential to improve how topic modeling techniques are used to predict, plan, and understand the evolution of software, and will inform the design of tools that support software engineering activities such as feature location, expertise identification, and bug detection.