Longitudinal changes in stream invertebrate assemblages of Grand Teton National Park, Wyoming

1. High elevation ecosystems are predicted to be strongly impacted by climate change; however, little is known of extant biodiversity in mountain streams. For this study, five streams in Grand Teton National Park, Wyoming were sampled along a longitudinal gradient to establish a baseline of invertebrate assemblages and environmental conditions. Five Surber samples were collected from low, middle and high elevation sites along each stream. 2. Nearly 10 000 ind m(-2) lived in these streams on average, but the density (mixed effects model, P = 0.54) and richness (P = 0.18) of invertebrates did not vary significantly by elevation. Total density of invertebrates was positively related to the amount of visible biofilm (ANOVA, P = 0.03) and oxidation-reduction potential (P = 0.05) and taxa richness was negatively related to specific conductivity (P = 0.009). 3. Invertebrate assemblages and environmental conditions were more similar at low versus high sites when compared using non-metric multidimensional scaling and tests of multivariate dispersion indicating that higher elevation sites harboured more environmental and species diversity. 4. These results can help target which aquatic invertebrates to monitor as stream temperatures rise, and highlight the biotic and abiotic factors that structure aquatic ecosystems in the Teton Range of Grand Teton National Park.