Meta-approaches to understanding diversity, including meta-populations and meta-communities, have created a paradigm shift in ecological research, including in stream ecosystems. Both of these frameworks emphasize the major role that organismal dispersal plays in generating and maintaining biodiversity patterns because dispersal links processes at local scales to processes at larger spatial scales. Fundamental to the application of meta-approaches is an understanding of dispersal. Ecologists working in stream systems use various methods to measure or estimate the dispersal of aquatic organisms. More direct measures include mark-recapture techniques and the use of various nets and traps. Due to the difficulty of directly monitoring the dispersal of aquatic organisms, particularly smaller taxa, organismal-based dispersal proxies such as traits-based approaches and population genetics can be used to infer dispersal patterns. Graph-based proxies that rely on the spatial distribution of sampling sites can also be used to infer dispersal in stream networks. While experimental approaches—including the direct manipulation of dispersal—have been employed less often than observational approaches, they have been able to mechanistically link dispersal rates and patterns to patterns in observed biodiversity. Likewise, theoretical approaches that include mathematical and simulation modeling have been able to conduct in silico experiments to test scenarios that are impractical or impossible to conduct in real-world systems. Here we provide a brief introduction to these techniques, highlight some of the insights that they have enabled, and discuss their importance in bringing meta-approaches to the study of stream ecosystems.

In this chapter, we provide an introduction to the study of dispersal from the perspective of its importance for meta-approaches in stream ecology that briefly touches on the conceptual importance of studying dispersal and on the techniques used to measure or estimate dispersal. In reviewing literature to include in this article, we chose to focus on fine-scale work performed at a maximum scale of a few adjacent watersheds because these studies best illustrate the approaches and techniques for the study of dispersal. However, a considerable amount of work also exists that applies meta-population and meta-community theory to large-scale biogeographic biodiversity patterns. Thus, our work here is not meant to be an exhaustive review of the literature on dispersal in stream networks, but to serve as an introduction to the various techniques used to understand the dispersal of stream organisms. Additionally, while the focus of this article is mainly dispersal in stream meta-populations and meta-communities, these are relatively new fields of study. Multiple foundational papers on dispersal in stream networks that we included here do not directly address meta-population or meta-communities. These older works are, however, crucial for an introduction to the topic, and the study of dispersal would be much diminished without the groundwork that these works provided.