Multiple watershed alterations influence fish community structure in Great Plains prairie streams Joshuah S. Perkin 1 , Matthew J. Troia 1,† , Dustin C.R. Shaw 1 , Joseph E. Gerken 2 , Keith B. Gido 1 1 Division of Biology, Kansas State University, 116 Ackert Hall, Manhattan, KS 66506, USA 2 Kansas Cooperative Fish and Wildlife Research Unit, Division of Biology, Kansas State University, 205 Leasure Hall, Manhattan, KS 66506, USA Accepted for publication September 29, 2014 Abstract – Stream fish distributions are commonly linked to environmental disturbances affecting terrestrial landscapes. In Great Plains prairie streams, the independent and interactive effects of watershed impoundments and land cover changes remain poorly understood despite their prevalence and assumed contribution to declining stream fish diversity. We used structural equation models and fish community samples from third-order streams in the Kansas River and Arkansas River basins of Kansas, USA to test the simultaneous effects of geographic location, terrestrial landscape alteration, watershed impoundments and local habitat on species richness for stream-associated and impoundment-associated habitat guilds. Watershed impoundment density increased from west to east in both basins, while per cent altered terrestrial landscape (urbanisation + row-crop agriculture) averaged ~50% in the west, declined throughout the Flint Hills ecoregion and increased (Kansas River basin ~80%) or decreased (Arkansas River basin ~30%) to the east. Geographic location had the strongest effect on richness for both guilds across basins, supporting known zoogeography patterns. In addition to location, impoundment species richness was positively correlated with local habitat in both basins; whereas stream-species richness was negatively correlated with landscape alterations (Kansas River basin) or landscape alterations and watershed impoundments (Arkansas River basin). These findings suggest that convergences in the relative proportions of impoundment and stream species (i.e., community structure) in the eastern extent of both basins are related to positive effects of increased habitat opportunities for impoundment species and negative effects caused by landscape alterations (Kansas River basin) or landscape alterations plus watershed impoundments (Arkansas River basin) for stream species. Key words: watershed; impoundments; fish community; Great Plains; streams Introduction Lotic freshwater ecosystems are strongly influenced by terrestrial land use alterations involving human extraction and exploitation of ecosystem goods and services (Likens et al. 1978; Richards et al. 1996). Agricultural land cover in particular contributes to reduced habitat suitability and degraded integrity of fish communities in surrounding streams (Wang et al. 1997). Such strong linkages between terrestrial land- scape alterations and stream biota are mediated by cascading mechanisms involving hydrologic connectivity, or the movement of matter, energy and organisms through stream corridors (Pringle 2001). The mechanisms that maintain hydrologic connectiv- ity include hydrology, geomorphology, erosion and deposition, such as run-off, channel shape, sediment movement and substrate composition respectively. These elements collectivity represents the land cover cascade (LCC), a framework used to quantify the transfer of land-cover-disturbance effects to stream biota such as fishes or aquatic invertebrates (Burcher et al. 2007). These landscape alterations have been implicated in the altered distributions of aquatic biota Correspondence: Joshuah S. Perkin, Department of Biology, Tennessee Technological University, 1100 N. Dixie Avenue, Cookeville, TN 38505, USA. E-mail: jperkin@tntech.edu † Present Address: Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA doi: 10.1111/eff.12198 1 Ecology of Freshwater Fish 2014 Ó 2014 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd ECOLOGY OF FRESHWATER FISH