6533b7cefe1ef96bd1257a6b

RESEARCH PRODUCT

Eresus kollari (Araneae: Eresidae) calls for heathland management

subject

description

Northwest Europe’s largest heather-dominated sandy habitats are located in the nature reserve Lu¨neburgerHeide, Germany. Yet, even these appear to be losing their ability to support some of their stenotopic species such as theladybird spider, Eresus kollari Rossi 1846, and are thus becoming increasingly important for the preservation of thesespecies. The habitat requirements of this endangered spider species were investigated in order to obtain data that will helpstabilize the last remnants of the species’ population in northwest Germany. Several heathland habitats were surveyed bypitfall trapping during the mate-search period of the males. Two statistical methods were applied: logistic regression andboosted regression trees (BRT). Both methods showed that three habitat variables are of prime relevance in predicting theoccurrence of E. kollari: a) thickness of the organic layer (a negative effect), b) soil temperature at a depth of 10 cm, and c)Calluna cover in the herb layer (both have positive effect). Our results show that choppering (removing above-groundbiomass and most of O-layer) and burning are likely appropriate heathland management measures for the conservation ofE. kollari. Such measures improve the species’ habitat quality by creating a heterogenic (small-scaled) heathland structurewith suitable microhabitats. As Calluna heathlands show a clear senescence of the dominant heather, it is essential thatthose habitat patches be conserved. Further measures, such as transfer experiments, are recommended. Northwest Europe’s largest heather-dominated sandy habitats are located in the nature reserve Lueneburger Heide, Germany. Yet, even these appear to be losing their ability to support some of their stenotopic species such as the ladybird spider, Eresus kollari Rossi 1846, and are thus becoming increasingly important for the preservation of these species. The habitat requirements of this endangered spider species were investigated in order to obtain data that will help stabilize the last remnants of the species’ population in northwest Germany. Several heathland habitats were surveyed by pitfall trapping during the mate-search period of the males. Two statistical methods were applied: logistic regression and boosted regression trees (BRT). Both methods showed that three habitat variables are of prime relevance in predicting the occurrence of E. kollari: a) thickness of the organic layer (a negative effect), b) soil temperature at a depth of 10 cm, and c) Calluna over in the herb layer (both have positive effect). Our results show that choppering (removing above-ground biomass and most of O-layer) and burning are likely appropriate heathland management measures for the conservation of E. kollari. Such measures improve the species’ habitat quality by creating a heterogenic (small-scaled) heathland structure with suitable microhabitats. As Calluna heathlands show a clear senescence of the dominant heather, it is essential that those habitat patches be conserved. Further measures, such as transfer experiments, are recommended.