THE EFFECTS OF SPATIAL PATTERNS IN HABITAT QUALITY ON COMMUNITY DYNAMICS WITHIN A SITE

Metapopulation studies of single species have shown that the size and spatial arrangement of patches of assumed uniformly 'suitable' habitat can influence their population dynamics and persistence. We investiga ted whether variation in the spatial arrangement of 'suitable' habitat of varied quality within a single site can affect the abundance and p ersistence of interacting species. We accomplished this by extending a field-based spatial simulation model of four interacting species at t wo trophic levels (an endangered butterfly, its larval food-plant, and two ants). The habitat on sites with the same average and range of qu alities was rearranged to give varying degrees of local spatial hetero geneity or 'site ruggedness'. We found that the ant species that acts as host to the butterfly caterpillars decreased with site ruggedness. The impact on the butterfly was more substantial: it often failed to p ersist on very rugged sites. Despite being free-ranging over the whole area, the butterfly's persistence depends on the arrangement of habit at quality at a finer spatial scale, due to its interactions with spec ies possessing narrower habitat niches and more localized dispersal. R uggedness also influenced the rate of recovery of the host ant, and he nce community structure, for more than a century following the butterf ly's extinction.