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trees, and between and within individual leaves. Differences in infection levels between trees result from dif{Erences in
infection by individual species, with QE7 comprising differences early in the season and QE1 later in the growing season.
Leafmining is associated with increased fungal infection, and leaves with dead larvae have higher infections than those with
live larvae. However, neither mass nor survival of leafminers was affected by spore-injection of the three common endophytes.
One endophyte (Y 1) increased developmental thne. Other experiments show that oviposition is not associated with
leaves that are either' more or less likely to become infected with endophytes. Thus, leafmining activity appears to increase
infection frequency, probably by altering the surface of the leaf, but the endophytes themselves appear to have only weak
effects on leafminer development and survival.
Preliminary observational evidence :indicates that Arizona fescue in areas under intensive grazing by cattle and native
ungulates have higher frequency of Ac'rernonium starrii but not the p-endophyte. These results support our prediction that
endophytes that are only transmitted vertically are more likely to interact mutualistically with the plant and provide protection
against herbivores. Furore experiments will test the dependency of the mutualism on available resources to the grass and
controlled levels of herbivory. Similarly, experiments with seed-h_vesting ants show that Acremoni_ma-infected seeds are
less likely to be collected. Of the seeds that are harvested, E+ seeds are more likely than E- seeds to be discarded into reff_se
piles where germination success is higher than in surrounding areas.
SUMMARY
Endophytic fungi are diverse and ubiquitous in almost all woody and non-woody plants examined to date. The role
of endophytes in plant-herbivore, plant-plant, and plant-seed predator interactions in natural systems is still largely unex-
p]ored. Testable hypotheses and predictions, however, can be made about the direction and strength of the interactions based
upon mode of transmission and specificity of the fungi and plant.
ACKNOWLEDGMENTS
I thank Kyle Hammon and Dennis Wilson for preliminary data and Rindy Anderson, Carmen Febus, Dawn
Hagerman, Catherine Hudson, Terri Kingrey, Myrna Miller, and Franziska Schulthess for technical assistance. This work is
supported by NSF Grant BSR 91-07296 to SHE
LITERATURE CITED
CLAY, K. 1990.. Fungal endophytes of grasses. Ann. Rev. Ecol. Syst. 21: 275-297.
FAETH, S.H. 199t. Effect of oak leaf size on abundance, dispersion, and survival of the leafminer, Cameraria sp. nov.
(Lepidoptera:Gracillariidae). Envir. Ent. 20: 196-204.
KNOCH, T.R., I_ETH, S.H., and ARNOTT, D.L. 1993. Endophytic fungi alter foraging and dispersal by desert seed harvesting
ants. Oecologia 95: 470-475.
STRONG, D.R. 1988. Endophytic mutualism and plant protection from herbivores. Ecol. 69: 1.
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