Disentangling the influence of biotic and abiotic drivers on the distribution of individual species, or the composition of communities, is a fundamental challenge in ecology. Ecosystem engineers exist at an important nexus between biotic and abiotic forces, shaping the physical environment and often facilitating other species in the process. In freshwater ecosystems, net-spinning caddisflies (Trichoptera: Hydropsychidae) are abundant, widely distributed ecosystem engineers. Caddisfly silk nets and retreats have well documented positive effects on stream macroinvertebrates and microbial communities. However, because caddisfly distribution itself is also driven by the abiotic environment, their importance to biotic interactions is difficult to predict at the landscape scale. We sampled caddisflies and other macroinvertebrates across a 1.5km reach of Cherry Creek, MT to evaluate whether high resolution, georeferenced data on substrate type, substrate size, geomorphic units, current velocity, water depth, temperature, light, and dissolved oxygen or the presence of caddisflies best predicts macroinvertebrate community structure. We found that net-spinning caddisflies ranged widely in density (0-1200/m2) and abundance was highest in large substrates. We discuss how to use hierarchical modeling of species communities (HMSC) to explore the abiotic factors driving both the occurrence of an engineer of interest, such as net-spinning caddisflies, and associated macroinvertebrates across stream reaches. We then review the evidence for positive associations between caddisflies and their potential beneficiaries after accounting for the influence of the abiotic environment. Our work informs ideas about the spatially patchy importance of ecosystem engineering and advances the goal of understanding the interplay between biotic and abiotic drivers at scale.