Distribution and habitat suitability of two rare saproxylic beetles in Croatia - a piece of puzzle missing for South-Eastern Europe

Due to habitat loss and fragmentation, the hermit beetle, Osmoderma eremita species complex (Coleoptera; Scarabidae) and the European red click beetle, Elater ferrugineus Linnaeus, 1758 (Coleoptera: Elateridae) are considered threatened in many European countries. Their presence in a large part of South-Eastern Europe has been sporadically recorded and these findings are mainly historical. Here we present the most recent findings of both species, assembled mainly throughout this first systematic study aiming to collect data on the hermit beetle within mapping and monitoring activities of saproxylic species protected by the European Habitat Directive (Annexes II and IV of Council Directive 92/43/EEC) within the Mediterranean, Continental and Alpine biogeographical regions of Croatia, and current literature data. To facilitate mapping activities and species range monitoring to improve the proper management of suitable habitats, we created habitat suitability maps using recent findings for both species, and predicted distribution were overlapped and analysed with historical data and protected areas. Most of the individuals were captured using flight intercept cross-vein funnel traps baited with pheromone for the hermit beetle placed within natural forest dominated by oak, beech and montane beech-fir forests, on sites with and without any forest management. Among set of 11 environmental variables, autumn precipitation, spring mean temperature and slope contributed most to the beetle distribution models. Data analyses indicated that the European red click beetle has much wider environmental envelope in which it can occur and that the hermit beetle can be used as surrogate species for the European red click beetle.