Context-dependent sublethal hazard of glyphosate to non-target predators revealed by functional response analysis

Glyphosate, one of the most widely used herbicides globally, is a significant environmental contaminant that may affect non-target organisms crucial to ecosystem services, including biological pest control. While glyphosate targets the shikimate pathway in plants, which is absent in animals, there is increasing evidence that glyphosate induces sublethal effects on arthropod predators. However, the factors modulating these effects remain unclear. Here, we investigated how physiological context, specifically pre-treatment with the broad-spectrum antibiotic tetracycline, commonly used to experimentally alter host associated microbial communities, modulates the sublethal hazard of glyphosate-based herbicide (GBH) on the predatory behavior of adult female Pardosa wolf spiders. Predation efficiency was measured using functional response assays across varying prey densities. Our results showed that GBH significantly reduced the spiders' predation rates, confirming its sublethal toxicity. However, spiders pre-treated with antibiotics exhibited higher capture rates following GBH exposure compared to the GBH only group. These findings demonstrate that the sublethal hazard of GBH on predators is context-dependent and can be altered by antibiotic-sensitive processes (such as host-symbiont interactions). This study highlights the complexity of pesticide effects on ecosystem services and suggests that the functional response of non-target predators depends strongly on their physiological background.