The goal of our study was to investigate the interaction between the invasive mussel Limnoperna fortunei and benthic invertebrate communities at different spatial scales and under different environmental conditions. We analyzed the effects of L. fortunei on benthic invertebrate communities at different downstream distances (meters) from mussel beds and compared these trends in 2 rivers characterized by dissimilar chemical disturbance levels. In areas distant from L. fortunei beds, invertebrate composition at the 2 rivers differed strongly, probably in response to different levels of environmental pollution. In areas near L. fortunei beds, invertebrate composition at the 2 rivers was similar, suggesting that golden mussels have strong homogenizing effects on faunal makeup. We also found that facilitation was species specific and, in contrast to the general paradigm, weaker (rather than stronger) under more stressful conditions. Our results show that understanding the effects of L. fortunei requires accounting for scale- and species-specific effects.