Arthropod Colonisation of Trees in Fragmented Landscapes Depends on Species Traits

Effects of habitat fragmentation vary greatly between organisms. Traits such as dispersal mode and habitat preference may explain these differences. We predict that organisms with low dispersal abilities respond mainly to habitat isolation whereas aerial colonisers respond to the amount of suitable habitats at the landscape scale. To test these predictions 30 sites were chosen that varied independently in the level of isolation from woody habitats and in the percentage of woody habitats in 500 m circumference. At each site seven cherry trees were established. Overwintering arthropods were sampled using cardboard hides. Glue rings were attached around tree stems to distinguish between walking and aerial colonisers. As predicted for walking dispersers, earwig abundance was strongly affected by habitat isolation. In contrast, three species of ballooning spiders responded neither to glue rings nor to habitat isolation. Instead they were affected by habitat amount in accordance with their preferred habitats. These results strongly encourage the use of species traits to predict effects of landscape fragmentation on organisms. However, additional factors such as interactions between species groups need also to be taken into account.