Epsilon Archive for Student Projects

Abstract

The rare beetle Elater ferrugineus was sampled at 47 sites in the county of Östergötland, Sweden by means of pheromone-baited traps to assess its value as an indicator species for hollow oak stands rich in rare saproxylic beetle species. In addition Osmoderma eremita was sampled with the same method. These data were then compared against species survey data collected in the same sites by pitfall and window-trapping. Weighted odds ratio models revealed that both species co-occur with many red listed saproxylic beetle species, with E. ferrugineus being a somewhat better indicator for the rarest beetle species. Regression models showed that the conservation value of a site (measured as red list points or number of red listed species) increased with the number of specimens of E. ferrugineus and O. eremita caught. Accuracy of sampling by means of pheromone trapping turned out to be radically different for the two model species. E. ferrugineus traps put out during July needed to be up for only 6 days in order to gain full accuracy, whereas O. eremita traps needed to be out from early July to mid August in order to obtain full accuracy with one trap per site. By using E. ferrugineus or preferably both species as indicator species, effort spent in the field, and thereby the costs for saproxylic biodiversity sampling, could be greatly reduced compared with conventional methods, and the accuracy of classification of valuable habitat significantly improved.