In the reported experiment with detritivorous stream invertebrates, Fuge`re et al. (2012) offered one of five species of leaf litter reflecting a resource-quality gradient to a limnephilid caddisfly (Anomalocosmoecus sp.), an amphipod (Hyalella sp.), or both invertebrates together. Subsequently, they assessed litter decomposition rate by determining leaf consumption normalized for body-mass specific metabolic activity, using an index named Leaf Processing Efficiency (LPE) (McKie et al. 2008, 2009). Limnephilid caddisflies are capable of cutting through tough leaf tissue, whereas the amphipod is supposed to feed mainly on the margins of leaf pieces. Fuge`re et al. (2012) reason that these differences in feeding patterns would increase the overall consumption of leaf litter, when both species feed on the same leaves simultaneously. However, the magnitude of this diversity effect would depend upon resource quality. Both species would easily consume high-quality litter, but on recalcitrant litter, the total length of leaf margins could possibly limit Hyalella feeding. Therefore, shredding activity of Anomalocosmoecus might be necessary to permit Hyalella feeding on lowquality litter. As a consequence, competitive interactions were presumed to be most important on a high-quality diet that was easily degraded by microbes, and facilitative interactions would enhance resource consumption on the low-quality litter.