Increased habitat connectivity homogenizes freshwater communities: historical and landscape perspectives

1. Increases in habitat connectivity can have consequences for taxonomic, functional, and genetic diversity of communities. Previously isolated aquatic habitats were connected with canals and pipelines in the largest water development project in US history, the Columbia Basin Project (eastern Washington, USA), which also altered environmental conditions; however, the ecological consequences are largely unknown. 2. Using a historical dataset, we examined long-term patterns in zooplankton communities, water chemistry and clarity, testing the hypothesis that increased connectivity will result in taxonomic homogenization. Further, we tested contemporary drivers of communities using a comprehensive set of environmental and landscape variables. 3. Waterbodies were sampled for zooplankton community composition as well as physical and chemical variables inside and outside the Columbia Basin Project using methods consistent with historical studies. 4. We found significant declines in salinity...