Abstract
Pest regulation by natural enemies has a strong potential to reduce the use of synthetic pesticides in agroecosystems. However, the effective role of predation as an ecosystem service remains largely speculative, especially with minute organisms such as mites.Predatory mites are natural enemies for ectoparasites in livestock farms. We tested for an ecosystem level control of the poultry pest Dermanyssus gallinae by other mites naturally present in manure in poultry farms and investigated differences among farming practices (conventional, free‐range, and organic).We used a multiscale approach involving (a) in vitro behavioral predation experiments, (b) arthropod inventories in henhouses with airborne DNA, and (c) a statistical model of covariations in mite abundances comparing farming practices.Behavioral experiments revealed that three mites are prone to feed on D. gallinae. Accordingly, we observed covariations between the pest and these three taxa only, in airborne DNA at the henhouse level, and in mites sampled from manure. In most situations, covariations in abundances were high in magnitude and their sign was positive.Predation on a pest happens naturally in livestock farms due to predatory mites. However, the complex dynamics of mite trophic network prevents the emergence of a consistent assemblage‐level signal of predation. Based on these results, we suggest perspectives for mite‐based pest control and warn against any possible disruption of ignored services through the application of veterinary drugs or pesticides.
Highlights
| INTRODUCTIONPopulations and assemblages in natural ecosystems are shaped by the interaction of bottom-up forces (resource limitation) and topdown forces (consumer regulation) (Leroux & Loreau, 2015)
Populations and assemblages in natural ecosystems are shaped by the interaction of bottom-up forces and topdown forces (Leroux & Loreau, 2015)
Our study provided evidence for predation by mites on a major parasite in poultry farms, but this process did not unambiguously translate into an assemblage-level signal, which prevents us from inferring a major pest regulation service
Summary
Populations and assemblages in natural ecosystems are shaped by the interaction of bottom-up forces (resource limitation) and topdown forces (consumer regulation) (Leroux & Loreau, 2015). The link between a predation process and the associated service (pest control) is difficult to quantify at the scales of farms and agricultural landscapes, because it rarely emerges additively due to assemblage-level processes. Pest–predator interactions and the resulting control service at an ecosystem level are strongly modulated by landscape composition and configuration (e.g., landscape complexity in Perez-Alvarez, Nault, & Poveda, 2019, and Winqvist et al, 2011, forest cover in Librán-Embid, De Coster, & Metzger, 2017) These effects typically range from positive to negative within single agroecosystems, with no obvious rule. The dependence to the choice of indicators suggests that exploring the emergent properties of pest–predator assemblages is a good way to advance the understanding on how agricultural practices affect the pest control service Hematophagous arthropods such as midges, bedbugs or poultry mites cause significant damage in animal production, but few studies addressed their regulation by natural enemies. Farming practices interfere with this possible service, with organic farms probably being the most favorable: Does this predation differ from one farming practice to another?
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