Macroinvertebrates of Ash Meadows National Wildlife Refuge, Nevada

Authors: Lawrence E. Stevens, Robert J. Andress

Year: 2009 (xli)

Abstract

Aquatic and terrestrial macroinvertebrates are important sources of food for desert fishes; however, levels of macroinvertebrate biodiversity are known for relatively few landscapes in western North America. Here we report results of research on the invertebrate diversity of Ash Meadows National Wildlife Refuge (AMNWR) in southern Nevada. AMNWR supports at least 28 endemic plant and animal species, including 10 species of plants, 9 hydrobiid snails, 2 naucorid waterbugs, at least one (and possibly three) beetles, 5 fish, and one mammal, and other undescribed endemic species likely exist there. This is the highest concentration of endemic species known to us from a single synoptic valley in the United States. However, prior to the present study, most non-endemic aquatic and terrestrial macroinvertebrate taxa at Ash Meadows had not been inventoried, and their diversity had received little attention. High concentrations of endemic species also have been reported from other constant, harsh aquatic habitats, such as Montezuma Well (central Arizona) and Cuatro Ciénegas (Coahuila, Mexico), but levels of non-endemic macroinvertebrate diversity have not been explored in detail at those locations. The Nevada Test Site, northeast of Ash Meadows, has a relatively robust desert terrestrial macroinvertebrate fauna, but little springs habitat and few endemic species. The overall invertebrate fauna in AMNWR appears to be depauperate and is dominated by generalist taxa. Odonata collections revealed 31 species, a moderately high level of diversity for a relatively small, semi-isolated southern Nevada valley; however, all of the taxa detected were widely distributed. In contrast to aerially-dispersing species, terrestrial and fossorial taxa tended to be low in species richness: we detected only 13 species of ground beetles (Carabidae), 15 species of darkling beetles (Tenebrionidae), and only a single landsnail species. Spider collections from 2004-2005 also revealed a depauperate fauna, with at least 82 species in 61genera and 26 families, dominanted by Salticidae, but with an overall landscape-based species density of only 0.96 species/km2. The depauperate condition of AMNWR is surprising, given the high proportion of endemic species there, but is consistent with that of other low elevation desert and playa habitats in North America. We observed a strong negative relationship between non-native crayfish and native aquatic macroinvertebrate abundance, which underscores the importance of direct management and intervention of non-native species, as well as the need for a consistent monitoring program for endemic aquatic invertebrates.