History and management of the endemic Ambrysus of Ash Meadows, Nye County, Nevada

Authors: Shawn C. Goodchild, Michael S. Parker

Year: 2008 (xl)

Abstract

Spring systems within the Amargosa Valley, southern Nevada, support one of the highest densities of endemic species in North America, with at least 27 endemic species occurring within the Ash Meadows National Wildlife Refuge. Habitat isolation created by the matrix of springs, desert upland, and sodic soils compartmentalized non-volant aquatic invertebrates, which influenced speciation. Two species of Naucoridae, Ambrysus amargosus and Ambrysus relictus, are restricted to a few very small, low-flow springs. Severely altered by anthropogenic activity, these springs were on the verge of losing their thermally-endemic species. To address this issue, investigations were completed to determine habitat suitability for these insects. These investigations informed management actions, which included addition of appropriate substrate and bank vegetation management. As a result, populations of naucorids have dramatically increased. Substrate additions and increased primary production resulted in two- to three-fold increases in A. amargosus densities, and densities of associated invertebrate populations, in restored channels within the Point of Rocks system. In contrast, A. relictus populations have either declined or remained stable in unmanipulated spring habitats in the Warm Springs system. There are numerous interacting factors that still present challenges for successful management of naucorid populations and the habitats that sustain them, but they are not insurmountable. These include effects of management for other endemic species such as Assiminea, potential effects of invasive invertebrates such as crayfish and Melanoides, continual presence of a Devils Hole pupfish (Cyprinodon diabolis) refuge, and ongoing need for habitat maintenance. Overall, management for these aquatic invertebrates has been successful, and one of the few documented programs to manage for aquatic insects.