This study explores the relationships between peer-to-peer interactions and (1) group formation among students, (2) choice of research, and (3) course performance in an online asynchronous ecology course at a research-intensive university. Peer-to-peer interactions have been known to enhance learning experience for students in a wide array of contexts, including online courses. However, less is known about how these interactions shape the students' performance and their choice of research over the course of time. Most previous studies have focused on either large introductory-level courses, where peer-to-peer interactions are usually lower, or analyses across a large number of courses, which introduce additional sources of variance. To explore how online peer-to-peer interactions develop, influence course dynamics, and impact student success, we collected data from a single medium-sized ecology course about peer-to-peer interactions, course performance, and student demographics. The course was repeated over six different semesters with the same instructor, same teaching assistant (TA), and an unchanged course structure to maintain certain homogeneity. Average class size was 20-25 students, and the educational format required intense discussions and peer interactions. Adopting a network science approach to the analyses, we find that peer-to-peer interactions not only affect student performance, but also shape class-wide interactions (e.g., working group formation), and choice of course research topic. Understanding this interplay of peer-to-peer interactions, group formation, and choice of research is important in forging necessary skills in students for a variety of contexts, and through such insights might better shape teamwork and choice of research, which are very important for molding future scientists in the twenty-first century.