Herbivory is a disturbance that can affect the recruitment pattern and distribution of seedlings. Proximity to mature conspecifics is widely known to impact rates of herbivory due to specialist herbivores and disease. Habitat fragmentation also impacts species interactions, such as rates of herbivory, by isolating populations, affecting dispersal, and changing habitat edge. Within the broader literature, herbivory has previously been studied in relation to the distance from parent plant, and in relation to habitat fragmentation, but no studies to our knowledge have put these ideas together in the same system. To understand how habitat connectivity affects species interactions, and particularly herbivory, we established founder populations of two forbs and two grasses within a replicated landscape-scale experiment in longleaf pine savanna. The experiment manipulated connectivity by corridors, fragment shape, and distance to edge, while controlling for area of habitat fragments. We evaluated how both the distance from parent and the effects of fragmentation affected herbivory (measured as ratio of damaged to undamaged leaves) on recruits of these founder plants. We addressed two questions: (1)How does herbivory change with distance from parent plant? (2)How do habitat connectivity, fragment shape, and distance to edge influence the herbivory on longleaf pine savanna plants?
Results/Conclusions
We found major effects of distance from parent plant on herbivory. We found that plants further away from the parent plant had more herbivory in 3/4 of our species. Fragment shape and connectivity generally did not affect herbivory, though in one of our four cases connectivity decreased overall herbivory. Distance from habitat edge was a significant predictor of herbivory in one of our four species with herbivory decreasing toward the center of the patch and increasing near the center, while being marginally or not significant in the other three. These results suggest that landscape scale and local scale factors can be important for patterns of herbivory, but these operate differently depending on the species. Increased herbivory with increased distance from a parent plant is likely due to generalist herbivores, the experimental planting of the founder populations, or a combination of the two factors. Disturbances such as herbivory may drive differences in population dynamics of plants that are commonly seen as a result of proximity to parent plant and habitat fragmentation. Understanding herbivory is important for predicting how fragmentation processes may affect plant populations, particularly for species of conservation concern.