Impacts of exotic spider spillover on resident arthropod communities in a natural habitat

Abstract

1. The spillover of exotic predators from managed ecosystems into natural habitats may exacerbate the biodiversity losses caused by land-use intensification. 2. In the present study, the impacts of the exotic wandering spider Cheiracanthium mildei L. Koch in an oak woodland ecosystem adjacent to an intensively-managed agricultural system were examined. 3. Abundance and species richness of resident spiders and insects in oak branches were reduced in the presence of C. mildei. Contrary to expectations, C. mildei did not disproportionately affect other wandering spider species, but appeared to impact spiders from all tested functional groups. Numbers of herbivorous and predatory insects were also lower in the presence of C. mildei. 4. Although the apparent effects of this spider extend to multiple trophic levels in oak woodland, its voracity and relatively large size may ultimately strengthen herbivore suppression in the vineyard-oak woodland landscape.