Influence of road edges on herbivory and leaf size in Northeastern Brazil restinga vegetation

Urbanization drives anthropogenic edge influence, changing adjacent vegetation structure and communities and affecting ecological processes such as nutrient cycling, pollination, and herbivory. Insect herbivory is a key interaction between plant and insect species that directly and indirectly affects ecosystem function. Plant and insect species, edge influence, climate, and functional and structural traits of plants can influence herbivory. My objectives were to examine the relationship between herbivory and leaf size (mass, thickness, area, specific leaf area) and to determine whether leaf size and/or herbivory differed between edge and interior vegetation and between trees and shrubs. Leaf samples were collected along four edge and four interior transects at two anthropogenic edge study sites in Salvador, Brazil (Parque das Dunas and Guaibim). One tree branch and one shrub branch were collected at each of the eleven sampling points along each transect. In total, 1852 leaves were collected and measured by hand for thickness and mass. ImageJ software was used to estimate leaf area and percentage of herbivory and to calculate specific leaf area. Specific and non-specific leaf area was greater at edge environments, and a greater leaf area was related to a higher probability of herbivory being present on leaves. Herbivory presence and intensity (%) were greater at edges. These were consistent for plant groups (shrub/tree) and sites (Guaibim/Parque Das Dunas). Results indicate that there is a relationship between herbivorous insects and leaf size, and that these interactions are impacted by edge influence and external pressures such as potential reduced predator occurrence at edges. Future studies will be needed to pinpoint exactly what pressures are driving these relationships.