Dung beetles: functional identity, not functional diversity, accounts for ecological process disruption caused by the use of veterinary medical products

Abstract

The impact of veterinary medical products (VMPs) on dung beetles has been thoroughly investigated. However, less is known about the ecological consequences for the ecosystem processes performed by this fauna, especially in relation to functional diversity. We explored the impacts of the long-term use of VMPs on dung beetles from a functional standpoint. We compared two areas with a different kinds of pasture management (long-standing use of VMPs vs. no use of VMPs) over two seasons (autumn and spring). We analyzed the impacts of VMPs on dung beetle functional diversity (using 23 traits) and the ecological process of dung removal. We also examined the relationships between species richness and functional diversity indices. Moreover, we investigated which community attribute was the most important in terms of efficiently sustaining the ecological process of dung removal. Long-standing use of VMPs led to a loss of functional richness, but other functional indices were less affected. A strong correlation between functional richness and species richness showed a low level of dung beetle redundancy, suggesting a low level of resilience in the ecosystem under study. The impact of the long term use of VMPs on dung beetle community attributes in turn had negative effects on the ecological process under study, with a reduction in dung removal capacity of 70%. Interestingly, this ecological process was not driven by functional diversity as many studies have shown, but rather by functional identity, such as the richness in paracoprids, telecoprids and the biomass of large dung beetles. These results raise concerns because large dung beetles, paracoprid and telecoprid beetles are the most functionally efficient in terms of dung removal capacity. At the same time, they are the most vulnerable and the most prone to extinction. Hence, our findings underscore the need to closely restrict the use of VMPs in order to maintain viable and ecologically efficient dung beetle communities.