Riffle Beetle Communities of Perennial and Intermittent Streams in Northern Nevada, USA, with a New State Record forOptioservus castaneipennis(Fall) (Coleoptera: Elmidae)

Abstract

Long-lived, benthic macroinvertebrate taxa are often poorly represented in intermittent streams because the periodic lack of water eliminates colonization habitat for those invertebrates, especially among those for which burrowing is not part of their life history. In the western United States, elmid beetles, which do not burrow, have a multiple-year life cycle, and multiple species are often found coexisting, even in intermittent streams. The elmid beetle communities of 21 sites on eight streams in northern Nevada were examined to determine patterns of occurrence and their relation to water permanence in those streams. Samples were collected in June 2006, May 2007, September 2010, and July 2011. In two streams, no elmid beetles were collected, probably due to the habitat not being conducive to elmid beetle presence (mucky substrate). Among the perennial stream sites, one or two species were consistently dominant, and the relative abundances of species were similar throughout all years. In contrast, elmid beetles were often, but not always, absent from intermittent streams even when water was present, and species dominance was usually different among the years when elmid beetles were present in those streams. These data suggest a strong role of opportunistic colonization in intermittent headwater streams, with more stable communities fostered by perennial streams. Collection records are presented for Optioservus castaneipennis (Fall), new state record, which heretofore had not been reported from Nevada.