The consequences of biodiversity loss for vector-borne disease dynamics is a topic of increasing interest. Studies that address this issue typically focus on the diversity of the host, vector, or pathogen community. However, the diversity of organisms at higher trophic levels, such as predators, can also indirectly play a role in vector-borne disease dynamics through direct effects on the abundance or behavior of pathogen vectors. Our goal was to determine the impact of altered diversity within the predator community on the suppression of pathogen vectors.
Results/Conclusions
To address the role of predator diversity in vector-borne disease dynamics, we evaluated the impact of altered predator diversity on the abundance of an important vector of barley yellow dwarf virus in wheat, the Bird cherry-oat aphid (Rhopalosiphum padi). In field and greenhouse experiments employing a substitutive design, we created predator assemblages that varied in both the number and identity of species present. When we compared the effectiveness of predator assemblages consisting of a single predator species to that of assemblages with two or four predator species, we found that on average a diverse group of predators reduced vector abundance more so than single predator species. However, closer inspection revealed that this apparent benefit of diversity was actually driven by the presence of one particularly efficient predator species. Diverse predator assemblages were only more effective at vector suppression because they were statistically more likely to contain the most efficient species than treatments where only a single species was present. Therefore, we conclude that it is the identity of species in the predator assemblage, rather than diversity per se, that determines the size of the vector population, which may ultimately impact pathogen prevalence.