A limnephilid caddisfly larvae (Anomalocosmoecus sp.) removed from its case and an amphipod (Hyalella sp.) from Andean streams. Leaf litter of five different qualities was offered to these two detritivores in an experiment to test whether the stress-gradient hypothesis from plant ecology might apply to stream invertebrate communities. Photo and copyright: Patricio Andino. Fugère, V., Andino, P., Espinosa, R., Anthelme, F., Jacobsen, D. & Dangles, O. (2012) Testing the stress-gradient hypothesis with aquatic detritivorous invertebrates: insights for biodiversity ecosystem functioning research. Journal of Animal Ecology, 81, 1259–1267.Does stress, defined as a reduction in growth by external constraints, modify biodiversity effects on ecosystem functioning? That is, are diversity effects stronger under stressful, as opposed to favourable conditions? The study by Fugère et al. (2012) in this issue borrows the stress-gradient hypothesis from plant ecology to explore this issue in an aquatic detritus-detritivore system. Although they find weak support for their hypothesis, the study opens the door for future experimental and theoretical investigations into the role of stress in modifying the relationship between the diversity of animal communities and ecosystem processes.