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

Abstract

Abundances and occurrences of leaf-mining insects on 3 oak species, Quercus falcata, Q. nigra and Q. hemisphaerica, that vary in leaf persistence times were monitored. When densities and species richness are compared among oak species, no significant differences were found, as predicted by Rhoades and Cates'' and Opler''s hypotheses regarding leaf miners that feed on oaks with different leaf durations. Densities of leaf miners are significantly and negatively correlated with total N content of leaves, a result contradictory to Feeny''s study on lepidopteran species that feed on another oak. If leaf persistence or, more directly, N content, at all affects abundances and numbers of leaf mining species on oaks, the effect is probably inconsequential compared to that of parasitism, predation, abiotic factors and overwintering success. Significant variation in leaf miner densities within and between trees and season was found. Much of the variation within the 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.