EN
In central Europe, the endangered Rosalia longicorn Rosalia alpina (L.) has rarely been observed to develop in the wood of elms Ulmus sp.; however, this beetle has recently expanded into habitats formed by elms. The factors driving these changes are unknown in detail, but a potential one is the increasing amount of breeding material, namely, dead elm wood. Dutch elm disease, caused by the fungi Ophiostoma ulmi and O. novo-ulmi, by killing off elm trees, has created a supply of dead wood. The aim of this work was to assess the potential role of Dutch elm disease in the formation of habitats suitable for the endangered Rosalia longicorn. The health of four elm stands (Carpathians, SE Poland) was analysed and the pathogen responsible for elm death were determined by DNA sequence comparison. O. novo-ulmi — the causative agent of Dutch elm disease — was isolated from weakened and dying trees at all studied localities. In total, 30% of the elm trees were dead, 34% showed signs of dieback or were moribund, while some 36% showed no signs of dieback (N = 120). The presence of the Rosalia longicorn was recorded at all four studied localities. The use of elms as a host plant was long-term; dead trees served as a breeding material through the past 11 years. Our results indicate that O. novo-ulmi is playing an important part in the death of elms in Rosalia longicorn localities. Dutch elm disease, due to its wide distribution, may shape suitable habitats for Rosalia longicorn within the species' range. While the chronic nature of the disease contributes to the slow and inexorable death of these trees, it may at the same time be a factor promoting the long-term stability of Rosalia longicorn habitats.