The Role of Hemiparasites in Structuring Ecosystems

University Of Washington, Seattle WA

Investigators

Abstract

Adopting a new way to address an existing question often yields new insights or answers. This project focuses on hemiparasites - plants that obtain resources both by making their own via photosynthesis and by stealing resources from the roots of other plants - to understand direct and indirect effects between plants and their herbivores. The novel twist here is that plants mediate interactions among different trophic levels, determining how a plant parasite affects a plant predator and vice versa. The research will have direct application to the management and recovery of two rare species: the hemiparasite is federally listed as threatened and the herbivore is an endangered butterfly. The investigators will partner with federal and state agencies to restore both species. This research will also provide research training to a post-doctoral research associate, a graduate student, and an undergraduate student. All will be actively mentored in responsible conduct of research, field and lab data collection, analysis, and outreach. The organisms used in this study co-occur in grasslands of the Pacific Northwest US. Experimental mesocosms will be assembled that contain host plants, hemiparasites, and herbivores. Mesocosms will contain high or low numbers of plant species that can serve as hosts for hemiparasites. Hemiparasitism will be manipulated among plants, and herbivores will be allowed to feed on the hemiparasites in a subset of the mesocosms. Hemiparasite survival, biomass, and secondary chemistry will be measured to determine how they are affected by host community composition, and herbivore performance will be related to host plant community and to hemiparasite resources. Stable isotopes will be used to track fluxes of carbon and nitrogen from the host plant community to the hemiparasites, and through the hemiparasites to their herbivores. The research will exploit an ecologically understudied situation in which plants function both as producers and as consumers to provide new insights into how multi-trophic interactions structure ecosystems.