Countryside biogeography of moths in a fragmented landscape: Biodiversity in native and agricultural habitats

Studies of fragmented landscapes, especially in the tropics, have tradition ally focused on the native fragments themselves, ignoring species distribut ions in surrounding agricultural or other human-dominated areas. We sampled moth species richness within a 227-ha forest fragment and in four surround ing agricultural habitats (coffee, shade coffee, pasture, and mixed farms) in southern Costa Rica. We found no significant difference in moth species richness or abundance among agricultural habitats, but agricultural sites w ithin 1 km of the forest fragment had significantly higher richness and abu ndance than sites farther than 3.5 km from the fragment. In addition, speci es composition differed significantly between distance classes (but not amo ng agricultural habitats), with near sites more similar to forest than far sites. These results suggest that (1) different agricultural production reg imes in this region may offer similar habitat elements and thus may not dif fer substantially in their capacities to support native moth populations an d (2) that the majority of moths may utilize both native and agricultural h abitats and move frequently between them, forming "halos" of relatively hig h species richness and abundance around forest fragments. Correlations betw een species richness and the amount of nearby forest cover, measured over c ircles of various radii around the sites, suggest that halos extend approxi mately 1.0-1.4 km from the forest edge. The extent of these halos likely di ffers among taxa and may influence their ability to survive in fragmented l andscapes.