Habitat corridors are a conservation strategy commonly used to increase the movement of organisms across fragmented landscapes. Though corridors have been shown to increase the dispersal of many animals and plants, it remains unknown whether corridors also affect the ability of organisms to colonize newly available habitats. To address this question, we used replicated experimental landscapes to test the effects of connectivity and fragment shape on habitat colonization by a solitary, wood-nesting bee (Megachile rotundata). Each replicate landscape was composed of a center patch of open meadow habitat surrounded by four equally-sized (1 hectare) habitat patches within a matrix of dense pine forest. A 150 m habitat corridor connected a single peripheral patch to the center patch, and each of the unconnected patches had additional habitat added as “wings” or an extended footprint to control for the added area of the corridors. We released bees in the center patch of each replicate landscape and measured their colonization of nest boxes placed in each of the peripheral patches. We then followed bee occupation of nest boxes throughout the flight period and counted all brood cells produced by reproductive bees at the end of the study.
Results/Conclusions
We found that bees responded strongly to spatial aspects of the landscape. We found a significant effect of connectivity on initial bee occupation of nest sites (χ2 =4.51, p= 0.03) but no effect of patch shape (χ2 =2.46, p=0.12). At the end of the study, both the number of nests and cells in patches were significantly affected by connectivity (χ2=6.58, p=0.01; χ2=17.02, p>0.001) and patch shape (χ2=9.93, p=0.002; χ2=29.39, p<0.001), with higher numbers of nests and cells produced in connected and winged patches than rectangular patches. The abundance of floral resources, however, had no effect on bee occupation of nest sites (χ2=0.01, p=0.93) or brood cell production (χ2=0.3209, p=0.57). We conclude that both habitat connectivity and configuration play a large role in bee colonization of new habitat, and suggest that spatial factors should be considered in conservation designs for new bee habitat.