Habitat fragmentation is a primary threat to biodiversity. Fragmentation can affect abiotic conditions and can alter ecologically important plant-animal interactions such as insect herbivory. During summer 2007 we studied herbivory of an early-successional annual (Solanum americanum) in experimentally fragmented habitat patches at the Savannah River Site near Aiken, South Carolina. All patches have equivalent area, but connectivity (via corridors) and edge-to-area ratios differ between patches. Our study system is designed to test the impact of connectivity, isolation and edge effects on plant fitness and community restoration. We planted 640 S. americanum seedlings in plots spaced at discrete distances from habitat edges (1m, 13m, 25m, 38m). We monitored levels of leaf herbivory on each plant throughout the growing season. During summer 2008 we will extend this study with a paired planting design that controls for plant genotype and excludes herbivory from one of each pair of plants. This will permit an even sharper focus on landscape determinants of herbivory and plant fitness.
Results/Conclusions
Data from eight experimental landscapes show that characteristics of habitat patches alter patterns of herbivory, but not overall levels of herbivory. In patches with increased edge-to-area ratios, distance from edge is positively correlated with levels of herbivory; this is not the case in habitat patches connected by corridors or rectangular patches. These results suggest that differences in habitat patch shape on a large scale can affect an ecologically important plant-animal interaction.
