MODEL SELECTION FOR A SUBTERRANEAN TROPHIC CASCADE: ROOT-FEEDING CATERPILLARS AND ENTOMOPATHOGENIC NEMATODES

Conjecture abounds while evidence is limited concerning indirect protection afforded plants by carnivorous predators in terrestrial ecosystems, apropos of the Hairston-Smith-Slobodkin (HSS) hypothesis. We conducted a field experiment with a suspected trophic cascade. Could an entomopathogenic nematode protect bush lupine by killing root-feeding ghost moth caterpillars? The experiment measured survival of lupine seedlings as a function of density of hatchling ghost moth caterpillars in rhizospheres with or without the entomopathogenic nematode. We modeled lupine survival with a hierarchical family of “one-hit dose response” models to interpret the results of the experiment. We obtained maximum likelihood estimates of parameters and selected the best-fitting model using the Schwarz Information Criterion (SIC). The best model fit the data closely, and SIC model selection was consistent with classical likelihood ratio test results of models nested in the one-hit family. A parallel analysis performed upon a lo...