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Biodiversity in River Networks

networkSubstantial variation in dispersal exists between organisms that contributes to the structuring of ecological communities in space and time. We are carrying out a set of studies to understand the relative roles of habitat geometry and environmental filtering in shaping local community composition in riverine networks. We hypothesize that communities in more isolated branches of dendritic networks will primarily be structured by a species-sorting metacommunity model, while mainstem sections of dendritic networks will be structured by both local and regional processes, or a mass-effects paradigm.

Stream restoration often proceeds under the assumption that once habitat is re-built, subsequent establishment and maintenance of desirable communities will occur: “build-it and they will come”. Our work specifically addresses the interacting roles of local and regional processes in determining local community structure. Our investigations may help reveal how structure and maintenance of communities are affected by more than just local factors. By working in dendritic systems, our results will add much to the fields of restoration and conservation, particularly in aquatic systems which are the focus of many such efforts.

Major Findings:

  1. Invertebrate Community Structure in smaller streams are structured more by local environmental constraints than larger rivers (Brown & Swan 2010)
  2. Biodiversity is substantially higher in headwater streams, owing to higher rates of compositional turnover in regionally rare taxa (Swan & Brown 2014)
  3. River restoration has a higher potential to change biodiversity patterns in headwater streams than larger streams (Swan & Brown, in prep).