Microclimatic edge effects in a fragmented forest: disentangling the drivers of ecological processes in plant‐leafminer‐parasitoid food webs

Abstract

1. In forest fragments, microclimatic conditions differ between interior and forest edges and also vary with geographical orientation. These microclimatic variations could affect plant‐insect food webs and the ecological processes in which they are involved.2. We evaluated the effects of microclimatic conditions, and the direct and indirect effects caused by changes in plant resources and leafminer abundance on leafminer herbivory and parasitism in the interior, and north and south‐facing edges of Chaco Serrano forest fragments in central Argentina.3. In the interior, and north and south‐facing edges of six forest fragments, we recorded: microclimatic variables, plant resource characteristics, leaf‐mining larvae availability, and leafminer herbivory and parasitism at plant community level and in three species (Croton lachnostachyus, Cestrum parqui, and Solanum argentinum).4. Herbivory was higher in north‐facing edges compared to south‐facing edges, while parasitism was generally greater in edges than in the interior. Temperature fluctuations positively affected plant community herbivory (through changes in leafminer abundance) but negatively affected S. argentinum herbivory via changes in foliar area and leaf‐mining larvae availability. Lower humidity levels directly favoured parasitism at plant community level, whereas higher thermal variations enhanced the parasitism of S. argentinum leafminers. Greater solar radiation favoured parasitism of C. lachnostachyus leafminers.5. Our results highlighted idiosyncrasy of each studied system (plant community and focal plant species), which responded differently to microclimate, and showed that mechanisms triggering herbivory and parasitism were different. The interior, and north and south‐facing edges of these forest fragments may function as differential micro‐refuges for herbivores and parasitoids under global warming context.