<p>Benthic macroinvertebrate communities in riverine ecosystems are shaped by both local conditions and processes that occur at larger spatial scales. Most models of riverine community structure are grouped into either discrete or continuum conceptual models. However, there is much uncertainty in how these two classes of conceptual models apply to macroinvertebrate communities in the physicochemically consistent headwaters of spring-influenced rivers. We examined benthic macroinvertebrate community composition and biomass among local discrete geomorphic mesohabitats (riffles, runs, and pools) and along an upstream to downstream gradient in two spring-fed rivers in central Texas. We found that longitudinal distance from the spring source in the San Marcos River and mesohabitat conditions in the Comal River played a greater role in shaping taxonomic composition. Taxonomic richness did not vary with distance from springhead but was consistently lower in pool mesohabitats when compared to runs and riffles in both rivers. Compositional changes and patterns in beta diversity within mesohabitat types among study reaches indicated that replacement rather than richness differences was the main mechanism leading to patterns of beta diversity. We also found that a non-native snail (<i>Tarebia</i>) constituted the largest proportion of benthic macroinvertebrate density and biomass in several study reaches downstream from springheads in both rivers.</p>