The role of interspecific competition for ecosystem temporal stability: Experimental tests using laboratory protist microcosms

Understanding what makes ecosystems stable over time is a fundamental question in ecology. While previous research has shown that biodiversity can help stabilize ecosystems, much less is known about how basic ecological processes, like competition between species, affect ecosystem stability. This project will investigate how competition influences the ability of ecosystems to maintain consistent functions over time (i.e., ecosystem temporal stability), both within individual ecological communities and across larger, interconnected systems. Using fast-growing, single-celled organisms called protists in controlled laboratory experiments, this project will test new ideas about how competitive interactions and the order in which species arrive influence ecosystem stability over time. In addition to advancing scientific knowledge, the project will provide meaningful educational opportunities. Undergraduate students will design and conduct experiments as part of their coursework, and high school students and K–12 teachers will participate in lab-based research through established programs at Georgia Tech. Outreach activities will include public engagement at science festivals and community events. The project will also provide training for a postdoctoral researcher, a graduate student, and multiple undergraduate researchers. This project will explore the role of interspecific competition in shaping ecosystem temporal stability at both local (community) and regional (metacommunity) scales, using laboratory microcosms containing assemblages of competing bacterivorous protists as the model system. At the local scale, the project will investigate how competition influences species stability and asynchrony, and, in turn, ecosystem temporal stability, using a series of complementary experiments. It will test the hypothesis that competition significantly increases species asynchrony and ecosystem temporal stability only in communities with sufficiently high response diversity. In addition, the project will incorporate modern species coexistence theory into stability research by examining how species niche differences and relative fitness differences influence patterns of species stability and asynchrony. At the regional scale, the project will test the hypothesis that priority effects, where early-arriving species influence community outcomes, are an important mechanism driving asynchronous dynamics among local communities, thereby contributing to metacommunity-level stability. Collectively, this project will provide rigorous, mechanistic insights into the roles of competition in ecosystem temporal stability across spatial scales. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.