A 3-TROPHIC-LEVEL ANALYSIS OF THE EFFECTS OF PLANT HYBRIDIZATION ON ALEAF-MINING MOTH

We investigated relationships between host plant hybridization in the Quercus grisea x Q. gambelii species complex and the distribution and performance of a leaf-mining moth in the genus Phyllonorycter. In 2 ye ars at two sites Phyllonorycter densities were lowest on Q. grisea and increased through the categories of hybrid host plants to Q. gambelii . Direct host plant effects on Phyllonorycter performance were consist ent with Phyllonorycter distribution; unexplained mortality of larvae in the mines, which is often associated with direct plant effects, dec reased from Q. grisea through the hybrids to Q. gambelii. Plant hybrid ization influenced parasitism of Phyllonorcycter. Parasitism was densi ty dependent, and across all densities was higher on Q. grisea and Q. gambelli than on hybrid host plants.