Mowed orchards of the thermophyticum in Central Europe as vanishing refugia for steppe spiders

Orchards on slopes with southern exposure and calcareous substrates are typical of the thermophyticum area of the Bohemian Basin. Because these slopes have long been maintained by mowing, they support semi-natural dry grassland stands and scrublands. These slopes are no longer mowed, however, and recently have become overgrown with grasses and subsequently with shrubs and woody plants. Pitfall traps were used to compare the abundance and community composition of spiders in two abandoned orchard sites in Central Bohemia: an orchard meadow site and shrubs site. Spider abundance was significantly greater at the orchard meadow site. Of the 62 species captured at both sites, 25 were found exclusively at the orchard meadow site. Xerothermic species of steppe spiders were detected at the orchard meadow site. The difference in spider abundance and community composition between the two sites presumably reflects changes in the habitat structure.