Abundances and Diversity of Leaf-Mining Insects on Three Oak Host Species: Effects of Host-Plant Phenology and Nitrogen Content of Leaves

Abstract

We monitored abundances and occurrences of leaf-mining insects on three oak species, Quercus falcata, Q. nigra, and Q. hemisphaerica, that vary in leaf persistence times. When densities and species richness are compared among oak species, we found no significant differences as predicted by Rhoades and Cates' and Opler's hypotheses regarding leaf miners that feed on oaks with different leaf durations. Furthermore, densities of leaf miners are significantly and negatively correlated with total nitrogen content of leaves, a result contradictory to Feeny's study on lepidopteran species that feed on another oak. We conclude that if leaf persistence or, more directly, nitrogen content, at all affects abundances and numbers of leafmining species on oaks, the effect is inconsequential compared to that of parasitism, predation, abiotic factors, and overwintering success. We did find significant variation in leaf miner densities within and between trees and season. Much of the variation within and between trees may be attributable to ovipositional preference of adult females or secondarily to differential mortality of eggs or larvae. The within and between season variability appears to be caused by the specificity of some leaf miners to certain leaf stages, the build-up of densities through successive cohorts of multivoltine species, and large fluctuations in year-to-year densities of a few species.