Habitat fragmentation is a formidable threat to biodiversity worldwide. Maintaining connectivity among remnant habitat patches is a central management plan to promote biodiversity. Therefore, understanding how the spatial arrangement of habitat patches in landscapes affect functional connectivity for communities is a critical goal in conservation biology. Describing connectivity at large-scales in complex landscapes is challenging due to, for example, the influence of multiple connections or variation in matrix permeability. Recently, network analysis (graph theory) has been proposed as an effective tool to assess connectivity in such landscapes. Using this approach, we address how connectivity influences species composition of ant communities in open habitats across an ~80,000 ha landscape, the Savannah River Site, South Carolina. We sampled ants using pitfall traps in 72 clearcut patches interspersed in the landscape. This system is ideal for understanding the role of connectivity in community assembly because of the discrete nature of these patches and their variation in degrees of connectivity.
Results/Conclusions
Invasive fire ants, Solenopsis invicta, are often associated with displacement of native ant species. We found that fire ants were negatively related with species richness (P=0.01, r 2 =0.13). Neither species richness nor abundance of fire ants, were significantly associated with alpha centrality (a graph based measure related to patch connectivity), (P=0.86 and P=0.96, respectively). These findings suggest that ant diversity in this system may be primarily driven by within patch interactions (e.g., competition with fire ants) among species or microhabitat differences rather than dispersal limitation due to fragmentation of habitat patches.
