Distribution and habitat of Onconotus servillei (Orthoptera: Tettigoniidae) within its westernmost range (Bulgaria, Romania, Serbia): models and perspectives

Degradation and loss of natural habitats as a consequence of anthropogenic activities have resulted in the loss of almost half of the biodiversity on our planet. Habitat specialists are among the species that vanish first and thus they are useful bioindicators for habitat change. One of the biomes subjected to strongest anthropogenic impact is the steppe biome. In Europe, natural steppes are among the most threatened grasslands, especially along their western border along the Lower and Mid Danube. Consequently, many animal species inhabiting steppes have been threatened with extinction. This study focuses on Onconotus servillei – a bush-cricket strongly dependent on the distribution and quality of its steppe habitat and threatened in Europe. It is assessed as Endangered in EU28, Bulgaria and Romania, Critically Endangered in Serbia, and Extinct in Hungary. We collected all known distribution data and model the species ecological niche. Based on confirmed recent observations we compare the model distribution with the species’ habitat preferences and current distribution of steppe habitats in Bulgaria, Romania and Serbia. The received pattern is discussed in the light of conservation issues and the species’ bioindicator properties to assess habitat quality. We conclude that O. servillei should be considered as a good bioindicator species for threatened European habitats and thus as a candidate priority species and species of community interest in need of strict protection of the European Commission Habitats Directive (92/43/EEC) Annexes II and IV.