Dissertation Research: Moisture-mediated Predation in an Underground Trophic Cascade

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I am researching how moisture influences a multi-predator trophic cascade in asoil system. At my research site on the California coast, the entomophagous fungusBeauveria bassiana is the most potent predator of root-feeding insects in dry summersoil. During the rainy winter and spring, however, soil moisture increases sharply and theentomopathogenic nematode Heterorhabditis marelatus becomes the primary predator asB. bassiana decreases in predatory efficiency. Both prey on ghost moth (Hepialuscalifornicus) larvae, root-feeding herbivores that feed on the bush lupine Lupinusarboreus. The lupine shows increased growth, seed set, and survivorship in the presenceof the nematode, which preys on H. californicus that would otherwise eat the lupine'sroots. The wet-season interactions in this food chain are known as an important exampleof a terrestrial trophic cascade. My research seeks to develop a complete picture of thisfood web by understanding predation on the herbivore during the dry season, and the rolethat moisture plays in both predators' activities. I also propose testing whether the twopredators have equivalent impacts on the prey population, possibly leading to cascadesdue to different predators in the wet versus dry season.