Spatial distribution of orchid bees in a rainforest/rubber agro-forest mosaic: habitat use or connectivity

The spatial distribution of orchid bees was analyzed in a mosaic of tropical rainforest and rubber tree groves in the Atlantic coast of Brazil (ARRF), comparing abundances and species compositions between replicas of the following landscape elements: small and large forest fragments, and rubber tree groves. Species compositions responded to all of the factors examined (time, mosaic elements, and distances; P < 0.009). In contrast, total orchid bee abundance varied significantly only over time (P = 0.0001), but not among the different mosaic elements (P = 0.05). Fragment size and distances between the fragments have affected species composition and abundance of some few common species. Most local species were present in the rubber plantation, and several species were using this matrix as a source of odor. The seasonal quality shifting of this matrix (leaf fall) has had less influence on the spatial distribution of orchid bees than the distances between forest fragments and fragment sizes. Previous studies of forest fragmentation have shown very weak effects of matrix isolation in mosaics with 5 to 90 % of forest cover, which supports the generalized expectation that organisms with well-developed dispersal capacities can respond to much higher thresholds of forest fragmentation.