Context-dependent insect predation pressure on an avian ectoparasite.
Angela SalidoJesús VeigaJoaquín Luis Reyes-LópezFrancisco ValeraPublished in: Insect science (2023)
Context dependence arises when ecological relationships vary with the conditions under which they are observed. Context dependence of interactions involving parasites is poorly known, even if it is key to understanding host-parasite relationships and food web dynamics. This paper researches to which extent predation pressure on an avian ectoparasite (Carnus hemapterus) is context-dependent. Based on a predator-exclusion experiment, predation pressure on Carnus hemapterus pupae in the host's nest for three years, and its variation between habitat types are quantified. Variation in precipitation and NDVI is also explored as a likely cause of context-dependency. We hypothesize that predation pressure should fluctuate with such surrogates of food availability, so that interannual and intraannual differences may emerge. The number of nest with significant reduction of pupae varied widely among years ranging from 24% to 75%. However, average pupae reduction in nests where a significant reduction occurred did not vary between years. No differences in predation rates between habitat types were detected. Precipitation and NDVI varied widely between years and NDVI was consistently lower around nests on cliffs than around nests on trees and farmhouses. Parallels were found between variation in predation pressure and precipitation/NDVI at a wide scale (highest predation the driest year, and much lower the two rainier ones), but not at the nest scale. This paper shows clear context-dependent insect predation pressure on an ectoparasite under natural conditions, and that such interaction changes sign rather than magnitude between years. The causes for these variations require longer-term studies and/or well-designed, large-scale experiments. This article is protected by copyright. All rights reserved.
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