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

Studies of fragmented landscapes, especially in the tropics, have traditionally focused on the native fragments themselves, ignoring species distributions in surrounding agricultural or other human-dominated areas. We sampled moth species richness within a 227-ha forest fragment and in four surrounding 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 within 1 km of the forest fragment had significantly higher richness and abundance than sites farther than 3.5 km from the fragment. In addition, species composition differed significantly between distance classes (but not among agricultural habitats), with near sites more similar to forest than far sites. These results suggest that (1) different agricultural production regimes in this region may offer similar habitat elements and thus may not differ substantially in their capacities to support native moth populations and (2) that the majority of moths may utilize both native and agricultural habitats and move frequently between them, forming halos of relatively high species richness and abundance around forest fragments. Correlations between species richness and the amount of nearby forest cover, measured over circles of various radii around the sites, suggest that halos extend approximately 1.0-1.4 km from the forest edge. The extent of these halos likely differs among taxa and may influence their ability to survive in fragmented landscapes.