A perspective on the importance of within-tree variation in mortality risk for a leaf-mining insect

Within-tree variation in abiotic conditions can create a mosaic of fitness gradients for herbivorous insects. To explore these effects, we quantified the patterns of mortality of the solitary oak leafminer, <i>Cameraria hamadryadella</i> (Lepidoptera: Gracillariidae), which lives within leaves of white oak, <i>Quercus alba</i>. We found differential patterns of survival and larval feeding rate within the tree and in association with several abiotic factors: light levels, leaf nitrogen content, and canopy height. We suggest that the leaf scale microhabitat conditions are fundamental to plant-herbivore-enemy interactions because of the differential fitness effects on herbivores. Such effects would be missed by studies that average effects by whole plants. Our study population of <i>C. hamadryadella</i> is located within the Orland E. White State Arboretum of Virginia in Boyce, Virginia, USA