As streams and rivers around the world transition from perennial to intermittent, it is important to understand how freshwater communities respond to cycles of wetting and drying. Growing global datasets increasingly allow researchers to detect large-scale patterns of biodiversity change but often miss the nuances of site-specific temporal changes that occur as species colonize and are replaced through succession. Here we studied community development in two intermittent streams in the western United States – an aridland stream (AS) in Arizona and a Mediterranean stream (MS) in California. We sampled macroinvertebrates throughout a full flowing season at each stream, from rewetting to subsequent drying (total: AS=140 days, MS=210 days). The number of days flowing explained over 80% of total taxonomic richness in both streams, although the MS had higher total richness than the AS (236 vs 147 taxa) and approximately 5.5 more taxa per sample. Despite these inter-site differences, richness recovered at approximately the same rate in both streams (increasing by ~1.01 taxa/day). We also observed patterns of species replacement, as resistant taxa were supplanted by resilient taxa, even within families. For example, desiccation-tolerant stoneflies and blackflies appeared early in newly wetted habitats and were later replaced by closely related and functionally similar stonefly and blackfly species that had developed from eggs laid by aerially dispersing adults. Thus, taxonomic turnover was decoupled from functional turnover, especially in the AS. Overall we found surprising similarities in community assembly in the two streams despite different climate contexts and environmental filters. Examining small-scale colonization trajectories and species replacements is important because it can highlight the mechanisms underlying broader biodiversity patterns observed across landscapes.