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

我正在研究水分如何影响一个土壤系统中多捕食者的营养级联。在我位于加州海岸的研究地点，食虫真菌球孢白僵菌是夏季干燥土壤中最强大的食根昆虫捕食者。然而，在多雨的冬季和春季，土壤湿度急剧增加，昆虫病原线虫maarelatus成为主要捕食者asB。球孢菌的捕食效率降低。两者都捕食鬼蛾（Hepialuscalifornicus）幼虫，这是一种以灌木羽扇豆为食的根食食草动物。在线虫的存在下，羽扇豆的生长、结籽和存活率都有所提高，而这种线虫会捕食加利福尼亚锥虫，否则加利福尼亚锥虫就会吃羽扇豆的根。这个食物链中的雨季相互作用被认为是陆地营养级联的一个重要例子。我的研究旨在通过了解旱季食草动物的捕食，以及水分在两种捕食者的活动中所起的作用，来全面了解这个食物网。我还建议测试一下这两种捕食者对猎物数量的影响是否相等，这可能会导致在雨季和旱季由于不同的捕食者而导致的连锁反应。

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.