“…Streams above the tree line in the alpine zone exhibit substantial environmental heterogeneity over small spatial scales, due in large part to variable hydrological sources (Brown, Hannah, & Milner, 2007;Füreder, 2007;Hotaling, Finn, Giersch, Weisrock, & Jacobsen, 2017;Ward, 1994). With such extensive habitat diversity, it is no surprise that alpine streams also support high among-stream (β) diversity across multiple taxonomic scales and classifications, including macroinvertebrate species diversity (Brown et al, 2007;Finn, Bonada, Murria, & Hughes, 2011;Giersch, Hotaling, Kovach, Jones, & Muhlfeld, 2016;Jacobsen, Milner, Brown, & Dangles, 2012), macroinvertebrate genetic diversity (Finn, Khamis, & Milner, 2013;Finn, Zamora-Muñoz, Múrria, Sáinz-Bariáin, & Alba-Tercedor, 2014;Hotaling et al, 2019;Jordan et al, 2016;Leys, Keller, Räsänen, Gattolliat, & Robinson, 2016), and microbial diversity (Fegel, Baron, Fountain, Johnson, & Hall, 2016;Freimann, Bürgmann, Findlay, & Robinson, 2013a;Wilhelm, Singer, Fasching, Battin, & Besemer, 2013). The biodiversity of alpine streams is under threat, however, as rising ambient temperatures drive the ongoing decline of mountain glaciers and perennial snowfields worldwide, and with them, the loss of hydrological variation on local and regional scales (Hotaling, Finn, et al, 2017).…”