Interactions between habitat abundance and configuration: experimental validation of some predictions from percolation theory

Recent neutral landscape models derived from percolation theory predict tha t a landscape with sparse but contagious habitat coverage is functionally e quivalent to one with more abundant but randomly situated habitat patches. We tested this prediction in a field experiment that determined how habitat -patch abundance and configuration affect landscape use by animals. Using a 2 x 2 factorial design in a 25-m(2) landscape, we created four treatments by varying the ratio of habitat (grass) to non-habitat (sand) patches (10%: 90% vs 20%:80%) and the clustering of grass habitat patches (random vs cont agious). We then followed the movements of tenebrionid beetles (Coleoptera: Tenebrionidae) through these experimental landscapes and measured their pa thway characteristics. Our results were largely consistent with neutral-mod el predictions, in that the amount of habitat present had a greater influen ce than did habitat configuration and habitat abundance exerted its stronge st influence on movement behaviours when habitat was sparse, regardless of spatial pattern. However, we also detected interactions between the amount and spatial arrangement of habitat patches that reflected how beetles respo nded to certain landscape-level properties of different abundances and conf igurations of habitat: average habitat-patch size and the distance between patches were better predictors of beetle responses than were the average nu mber of patches or the amount of patch edge (perimeter) within a treatment. Because of such latent influences of landscape-level habitat properties, o ur results have important implications for conservation efforts that endeav our to preserve landscape function by maintaining some minimum amount of ha bitat coverage. Interactions between habitat abundance and configuration co mplicate the detection and definition of landscape function, illustrating t he need for a spatially realistic approach in habitat management.