Effect of landscape structure depends on habitat type in shaping spider communities of a natural mosaic of Eurasian forest-steppe

Despite the important ecological role of forest-steppes in nature conservation, information on the contribution of individual components to arthropod conservation is scarce. Furthermore, the effect of landscape structure on the arthropod composition of a natural mosaic of habitats has been largely understudied.We investigated the effects of habitat type and landscape heterogeneity on spider diversity in forest-steppes of Kiskunsag National Park, Hungary. We sampled ground-dwelling spiders using pitfall traps in the grasslands, forest edges and forest interiors along a gradient of landscape composition (forest amount) and configuration (edge length) within 18 landscapes.We collected a total of 22,550 adult specimens belonging to 153 species. The three habitats of forest-steppes showed a distinct community composition with a characteristic set of species traits. Xerothermic species of web-building spiders were primarily found in grasslands, whereas spiders with a preference for moisture habitats were in the forest interior. The forest edges had higher species richness than forest interiors. The trait diversity, measured as RaoQ, was the highest in grasslands, while the lowest in the forests. We found that the increasing amount of forests in the landscape positively affected species richness in grasslands but negatively in forest edges and interiors. Edge length did not have any effect on spider communities.Increased species richness in grasslands with the increasing amount of forests highlights that grasslands are more affected by spillover from the neighbouring forests than vice versa. Habitat type plays a more important role in shaping spider diversity of natural forest-steppe patches than landscape structure. However, landscape structure could modify the effect of habitat type. It emphasises the importance of habitat complementarity and therefore the high value of all components of the forest-steppe landscape.

Automated summary

Despite the importance of forest-steppes in nature conservation, there is limited information on the contribution of different habitats to arthropod conservation. We investigated the effects of habitat type and landscape heterogeneity on spider diversity in the forest-steppes, and found that grasslands, forest edges, and forest interiors each had distinct community compositions and species traits. The increasing amount of forests positively affected species richness in grasslands but negatively in forest edges and interiors.