Transient windows of connectivity in a dendritic river system. In this example, the out-of-network Euclidean distance separating two populations of a fish species (black X’s) in the river is short, while the actual in-network dispersal distance is much longer, preventing connectivity between the two populations. A third population exists in a small pool in the river’s floodplain and is completely isolated from populations in the river. Temporal windows of connectivity at varying frequencies, however, allow these populations to be connected through time. An annual flood (dark gray) would connect populations 2 and 3 each year, while a much rarer 500-year flood (light gray) would connect all populations. The frequencies of these transient windows of connectivity could have important impacts on metapopulation persistence, gene flow, and habitat occupancy for the species.