River networks act as ecological corridors, and a paper in this week's Nature exploits this key feature to show that they can be used to characterize patterns of fish diversity.

Rachata Muneepeerakul and colleagues in Princeton U and other institutes in the US and Europe use the Mississippi-Missouri river basin system as a model for large-scale spatial features of fish biodiversity. They draw on estimates of average dispersal behaviour and habitat capacities, calculated from average runoff production. It is the river's dendritic structure that contributes to the richness of local species, the species range and the between-community diversity.

The authors claim that their type of model could be applied in a range of ecosystems to link global climate change, for example, to biodiversity patterns.

The abstract says (citations omitted):

“River networks, seen as ecological corridors featuring connected and hierarchical dendritic landscapes for animals and plants, present unique challenges and opportunities for testing biogeographical theories and macroecological laws. Although local and basin-scale differences in riverine fish diversity have been analysed as functions of energy availability and habitat heterogeneity, scale-dependent environmental conditions and river discharge, a model that predicts a comprehensive set of systemwide diversity patterns has been hard to find. Here we show that fish diversity patterns throughout the Mississippi-Missouri River System are well described by a neutral metacommunity model coupled with an appropriate habitat capacity distribution and dispersal kernel. River network structure acts as an effective template for characterizing spatial attributes of fish biodiversity. We show that estimates of average dispersal behaviour and habitat capacities, objectively calculated from average runoff production, yield reliable predictions of large-scale spatial biodiversity patterns in riverine systems. The success of the neutral theory in two-dimensional forest ecosystems and here in dendritic riverine ecosystems suggests the possible application of neutral metacommunity models in a diverse suite of ecosystems. This framework offers direct linkage from large-scale forcing, such as global climate change, to biodiversity patterns.”