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

Abstract

In forest fragments, microclimatic conditions differ between interior andforest edges and also vary with geographical orientation. These microclimatic variationscould affect plant-insect food webs and the ecological processes in which they areinvolved.2. We evaluated the effects of microclimatic conditions, and the direct and indirecteffects caused by changes in plant resources and leafminer abundance on leafminerherbivory and parasitism in the interior, and north and south-facing edges of ChacoSerrano 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, whileparasitism was generally greater in edges than in the interior. Temperature fluctuationspositively affected plant community herbivory (through changes in leafminer abundance)but negatively affected S. argentinum herbivory via changes in foliar area andleaf-mining larvae availability. Lower humidity levels directly favoured parasitism atplant community level, whereas higher thermal variations enhanced the parasitism of S.argentinum leafminers. Greater solar radiation favoured parasitism of C. lachnostachyusleafminers.5. Our results highlighted idiosyncrasy of each studied system (plant communityand focal plant species), which responded differently to microclimate, and showedthat mechanisms triggering herbivory and parasitism were different. The interior, andnorth and south-facing edges of these forest fragments may function as differentialmicro-refuges for herbivores and parasitoids under global warming context.