Species dispersal along rivers and streams may have variable importance to metapopulation structure

The ability to prioritize habitats that have spatially varied contributions to species persistence can produce synergistic benefits for regional conservation efforts. However, conservation in spatially diverse landscape-networks requires considering dispersal asymmetry in the context of ecological connectivity and metapopulation persistence. By developing an approach based on metapopulation theory, this study prioritized the importance of habitat (as determined by the habitat quality and spatial position in networks) on metapopulation structure in mountainous streams. As a case study, we examined dispersal via overland and instream networks in a riverine mayfly Rhithrogena sp. cf. japonica in a mountain range of Southwest China. Compared to flow velocity, water depth, and instream nutrient-levels, water temperature was a key factor in determining local habitat suitability for R. sp. cf. japonica. Higher water temperature was linked to poor habitat suitability. Instream pathways were the main dispersal corridors compared with overland movement between tributaries for this mayfly. In basins on the east aspect of this mountain range, either monotonically increasing (i.e., never decreasing) or unimodal (i.e., with a single peak) patterns demonstrated the importance of riverine habitats that occur along elevational gradients. However, the importance of habitat appeared to show no definite patterns with elevation on the west aspect. In terms of metapopulation structure, local quality of habitat contributed more to the regional importance of habitat than its spatial position in the networks. The framework presented highlights that the importance of riverine habitats may be quite variable in species having directional dispersal networks across the fluvial landscape in mountainous areas. Results from this framework can serve as the basis to apply a mechanistic understanding to managing and protecting native populations through regional restoration actions.