Contrasting landscape effects on species diversity and invasion success within a predator community

Abstract

Aim: The role of landscape variation in shaping invasion success remains unclear, particularly for exotic predators. We examined whether native and exotic predators responded similarly or differently to ecological change at the landscape scale. Location: Vineyards and surrounding natural habitat in the Napa Valley, California, USA. Methods: We surveyed spider communities in vineyards throughout the Napa Valley and used regression analysis to examine the effects of landscape context (proportion of vineyard monoculture and proportion of developed land surrounding vineyards) on spider species richness and on numbers and proportions of exotic spiders. We also compared spider composition and dominance of exotic spiders between vineyards and surrounding natural habitat using non-metric multidimensional scaling (NMDS). Results: The success of the dominant exotic spider Cheiracanthium mildei was contingent on landscape context, and increased with proportions of vineyard and developed land in the surrounding landscape. Spider species richness and native spider abundance followed an opposing pattern. Cheiracanthium mildei was relatively unsuccessful near and in oak woodland, the primary type of natural habitat surrounding vineyards. Main Conclusions: Results show that anthropogenic landscape change can have contrasting effects on native and exotic predators and that landscape context can influence the relationship between habitat modification and invasion success. Results suggest that it may be possible to limit the spread of invasions by increasing the availability of habitat for native species. © 2012 Blackwell Publishing Ltd.