Species-specific effects of dung beetle abundance on dung removal and leaf litter decomposition

• Dung beetle species and abundance were manipulated in a factorial mesocosm experiment.
• Changes in dung removal and leaf litter decomposition due to microorganisms in soil were examined.
• Dung removal shows large increases with increased beetle biomass and beetle abundance.
• Leaf litter decomposition shows limited increases with increased beetle biomass and abundance.
• Observed abundance effects vary depending on beetle species.

In grazed ecosystems, coprophagous beetles are known to play an important role in nutrient cycling, but interactions between species identity and dung beetle abundance on soil processes remain unclear. We conducted an outdoor mesocosm experiment to investigate the effects of three dung beetle species at four levels of abundance on dung incorporation into the soil. In addition we assessed indirect effects of dung beetle activity on leaf litter decomposition by microorganisms in soil. Both dung removal and leaf litter mass loss were positively correlated with initial dung beetle biomass and beetle abundance across species. However, the magnitude of beetle-induced increases in litter mass loss was very small compared to the magnitude of beetle effects on dung removal. Beetle effects on dung removal and litter decomposition also showed significant abundance × species interactions, with strongest responses observed for Colobopterus erraticus Linnaeus. Our findings highlight the importance of interactive effects between species identity and abundance on dung removal and provide the first demonstration of indirect dung beetle effects on leaf litter decomposition in soil.