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

University Of California-Davis, Davis CA

Investigators

Abstract

I am researching how moisture influences a multi-predator trophic cascade in a soil system. At my research site on the California coast, the entomophagous fungus Beauveria bassiana is the most potent predator of root-feeding insects in dry summer soil. During the rainy winter and spring, however, soil moisture increases sharply and the entomopathogenic nematode Heterorhabditis marelatus becomes the primary predator as B. bassiana decreases in predatory efficiency. Both prey on ghost moth (Hepialus californicus) larvae, root-feeding herbivores that feed on the bush lupine Lupinus arboreus. The lupine shows increased growth, seed set, and survivorship in the presence of the nematode, which preys on H. californicus that would otherwise eat the lupine's roots. The wet-season interactions in this food chain are known as an important example of a terrestrial trophic cascade. My research seeks to develop a complete picture of this food web by understanding predation on the herbivore during the dry season, and the role that moisture plays in both predators' activities. I also propose testing whether the two predators have equivalent impacts on the prey population, possibly leading to cascades due to different predators in the wet versus dry season.