Aquatic insect diversity in streams across a rural–urban land-use discontinuum.

Urbanization negatively impacts the diversity of aquatic insect assemblages in headwater streams and can lead to the homogenization of insect communities at the regional level. However, less is known about the impact of urbanization on insects in headwater streams within smaller cities that have significant upstream portions outside of urban land use. We collected insects monthly from April to September in 2014 and 2015 from five streams that flowed from rural upstream through urban downstream land use, plus two rural reference streams, in Greater Binghamton, New York, in the northeast USA. While urbanization was associated with lower insect taxonomic richness ( α ¯ ) and elevated stream water conductivity, the regional diversity (γ) was similar among urban and rural land use. This corresponded to higher dissimilarity among urban sites (β) than among rural sites. To our knowledge, this is the first report of higher urban stream insect community β-diversity. Our results suggest that urbanization in this medium-sized city negatively impacts stream insect richness, but the change of community assemblages is not homogenous across the urban landscape. Connectivity between upstream rural sites and downstream urban sites may provide some relief from the impacts of urbanization in smaller cities. [ABSTRACT FROM AUTHOR]