How does the community structure of dung beetles affect ecosystem functions? Modeling of secondary seed dispersal and seedling establishment

Dung beetles are associated with diverse ecosystem functions. However, their populations are declining globally, raising concerns about the loss of ecosystem functions. Among these services, secondary seed dispersal is crucial for plant recruitment and movement. To reveal the relationship between community composition and ecosystem function, I developed a novel mathematical model simulating seedling establishment that accounts for seed dispersal by two functional groups (tunnelers and rollers), seed predation, and among-seedling competition. The model revealed that when seed predators were absent, rollers contributed more to seedling establishment than tunnelers; consequently, communities with a high proportion of rollers and a low proportion of tunnelers maximized the number of established seedlings. Under high predation pressure, tunneler-abundant communities yielded greater seedling establishment. Under intermediate predation pressure, the relative contributions of the two functional groups depended on the intensity of among-seedling competition: tunnelers enhanced establishment when competition was weak, whereas rollers excelled when competition was strong. This study provides the first mathematical framework for dung beetle-mediated secondary seed dispersal, advancing our understanding of the links between community composition and ecosystem functioning. These findings offer critical insights for anthropogenic biodiversity management, such as the conservation and introduction of dung beetle communities.