Diversity and distribution of spiders (Arachnida: Araneae) in dry ecosystems of North Rhine-Westphalia (Germany)

The present study provides a robust data set for ecological planning and conservation of dry ecosys- tems in western Germany in general and North Rhine-Westphalia in particular. We summarised all available data from recent publications that dealt with spiders in dry ecosystems of North Rhine-Westphalia. Additionally, so far unpublished results of a detailed investigation regarding spiders in sand habitats of the Westphalian Bay that was conducted between 2006 and 2008 are presented. The analysis focussed on the habitat types according to Annex I of the EU Habitats Directive and related habitats. The investigation areas were scattered in the federal state of North Rhine-Westphalia. The data set comprised a total of 84436 individuals from 371 species and 28 families. Overall, an endangerment status is assigned to 68 species. Of these, 12 spiders are in imminent danger of becoming extinct. Two species, Erigonoplus globipes and Meioneta simplicitarsis, are believed to be extinct in North Rhine-Westphalia. Seven species (Dictyna major, Mastigusa arietina, Micaria formicaria, Styloctetor romanus, Thanatus striatus, Theridion uhligi and Xysticus ferrugineus) are new to the arachnofauna of North Rhine-Westphalia. In Germany, dry ecosystems, such as nutrient-poor sandy grasslands, dry heaths and semi-natural dry grasslands and scrubland facies on calcareous substra- tes are highly endangered (RIECKEN et al. 2006) and are listed in Annex I of the European Habitats Direc- tive as priority habitat types (BALZER & SSYMANK 2005). Due to increasing cultivation, especially during the past 50 years, and the lack of disturbance (drif- ting sand, grazing, fire) the area of dry ecosystems has decreased considerably in northern and western Germany (DRACHENFELS 1996, VERBUCHELN & JOBGES 2000, JENTSCH et al. 2002, KRATOCHWIL