Using Species Distribution Models to Guide Field Surveys for an Apparently Rare Aquatic Beetle

Abstract

Abstract Surveying for rare animals can be difficult but using models to predict suitable habitat can guide sampling efforts. We used models to predict suitable habitat for the Narrow-footed Hygrotus Diving Beetle Hygrotus diversipes (diving beetle hereafter), a dytiscid beetle that is known from 10 streams in central Wyoming. The diving beetle was a category-2 Candidate species for listing as Threatened or Endangered in the Endangered Species Act between 1989 and 1996, and was petitioned for listing in 2007, 2008, and 2013. Suitable habitat for the diving beetle was predicted using Maximum Entropy and Random Forest models in Wyoming. Both models predicted that the diving beetle was more likely to occur in intermittent streams with a gentle gradient, shallow water table, variable precipitation pattern, and high soil electrical conductivity, and in the warmest areas of Wyoming. We conducted surveys for the diving beetle at sites where the species had previously been found, and in new areas that were predicted suitable by our models to evaluate whether it is more widely distributed than indicated by previous estimates. We sampled beetles using dip nets and bottle-traps, and assessed water quality at each site. We collected the diving beetle at three sites in central Wyoming between 2010 and 2012 in small, alkaline, intermittent streams with disconnected pools. The aquatic habitat of the diving beetle is dynamic and our results suggest that annual precipitation patterns have a strong influence on the biogeography of this habitat. Our results also suggest that maintaining the hydrologic integrity of prairie streams in Wyoming is vital to the conservation of the diving beetle.