Intraspecific aggregation from local dispersal mediates transient species coexistence in plant communities

Understanding how niche and spatial processes jointly maintain biodiversity remains a key challenge in ecology. Using a spatially explicit cellular automaton framework, we analyzed plant coexistence dynamics across flooding gradients by simultaneously incorporating species hydrological niche, mixed dispersal strategies (ratios of global seed dispersal to local clonal growth), and intra- and interspecific neighborhood competitive interactions. Our results reveal three fundamental insights: First, niche differentiation along hydrological gradients enables stable coexistence even when intraspecific competition is weaker than interspecific competition. Second, local dispersal reproduction confers competitive advantage in heterogeneous habitats by forming spatial aggregations and minimizing propagule wastage. Third, while local dispersal-driven intraspecific aggregation prolongs coexistence by alleviating interspecific competitive interactions, it merely delays rather than prevents competitive exclusion, underscoring the transient nature of spatially-mediated coexistence. These findings advance coexistence theory by integrating environmental gradients with spatial demographic processes, and provide critical mechanistic insights for wetland biodiversity conservation.