In natural ecosystems, community dynamics are shaped by diverse interactions operating through ecological and reproductive processes. Ecological processes, such as growth and resource competition, generate niche and fitness differences that jointly determine competitive outcomes. On the other hand, reproductive interference—where one species harms another through interspecific reproductive processes—can generate positive frequency-dependency in community dynamics.

Although the interplay between ecological and reproductive processes is widely explored in theorical studies, empirical examination has largely lagged behind theory, likely owing to the isolation between the two research fields. In this study, we integrated the two perspectives to empirically examine whether and how two congeneric plant species (Commelina species) coexist under simultaneous ecological competition and reproductive interference. We combined empirical and theoretical approaches: We first developed a mathematical model describing the ecological and reproductive dynamics of the two species; we then conducted manipulative experiments to estimate model parameters empirically, and simulated the parameterized model to predict long-term dynamics.

Our empirically-calibrated model indicated (i) competitive superiority of one species (C. communis) over its congener (C. c. f. ciliate), and (ii) mutual reproductive interference between them (i.e., positive frequency-dependence of seed production). However, the observed reproductive interference was insufficiently strong to create pronounced contingency of community dynamics on initial conditions, and predicted outcomes largely matched those derived from ecological processes alone. Such non-strict reproductive interference is likely to reflect reproductive assurance strategies via pre-emptive selfing in Commelina species.

This study is among the first to demonstrate empirically the combined roles of ecological and reproductive processes in driving long-term community dynamics, highlighting the potential that effects of reproductive interference are overridden by those of ecological niche and fitness differences.