While substantial effort has been invested in modelling changes in species distribution with climate change, less attention has been given to how climate warming will affect interactions among co-occurring species, and the cascading functional consequences. In this study, realistic dung beetle communities were subjected to an experimental warming treatment and the net effect on the functions of dung decomposition (in terms of dung mass) and plant productivity (in terms of biomass production of ryegrass grown on soil from underneath the dung pats) were examined. A priori, we hypothesized that the largest tunneling species would be functionally dominant, and be differently affected by experimental warming compared to pat-dwelling, smaller species. In terms of dung decomposition, the largest beetles did prove to be the functionally most important, with the qualitative pattern unaffected by experimental warming. In contrast, for plant productivity all species appeared equally important under ambient conditions. However, the effects of single species on plant productivity were reduced as temperature increased: In a warmed climate, a combination of both tunneling and pat-dwelling species came the closest to returning ecosystem functioning to levels found in the ambient treatment. These results suggest different roles for different species, and highlight the importance of maintaining multiple species within an ecosystem – particularly when systems are perturbed.