Research

In our lab we combine theoretical models with laboratory or field observations and experiments to understand the factors affecting the dynamics of animal populations. We are interested in how stage-specific processes, life-history traits and behaviors of individuals translate into effects on dynamics at the population level.

Current Projects:

	Amphibian Disease Dynamics in a Fragmented Landscape Funded by NIH National Institute of Environmental Health Sciences grant: R01 ES12067-01, $2,250,000, 2002-2007. The mountain yellow-legged frog, Rana muscosa, was previously abundant in lakes throughout the Sierras. In the last several decades its populations have become fragmented due to the introduction of non-native trout, which prey on frog eggs and tadpoles (see www.mylfrog.com for more details). The previoulsy abundant frog populations are now dwindling. In the last few years, a newly identified fungal pathogen, Batrachochytrium, poses a new threat to this species, and to amphibians worldwide (see www.amphibiaweb.org for more information on amphibian declines). We plan to quantify the effects of this fungus on the frog metapopulation through (a) developing a spatially-explicit model, (b) experimentally studying the details of the disease transmission and other factors that may affect the persistence of the fungus in the environment, and (c) measuring dispersal of the frogs and movement patterns of the disease throughout the landscape. People Involved and their role in the project: Cherie Briggs: Population modeling Martha Hoopes: Modeling Roland Knapp: Frog ecology and surveys Craig Moritz: Frog population genetics John Parker: Amphibian pathology Lara Rachowicz: Disease transmission and ecology John Taylor: Chytrid biology and genetics Vance Vredenburg: Frog dispersal, behavior and ecology
	Productivity and intraguild predation in orchard crop systems Funded by USDA CREES grant 2003-35316-13767, $200,000, 2003-2006. Pear psylla is an important pest in pear orchards that is attacked by a number of generalist predators, some of which also feed on each other, an interaction called intraguild predation. We seek to understand how common intraguild predation is in pear orchards and how likely intraguild predation is to lead to release of pear psylla from effective biological control.
	Princeton Monograph in Population Biology on Consumer-Resource Dynamics With Bill Murdoch and Roger Nisbet at UC Santa Barbara, I have just completed a monograph summarizing our work and others' on the dynamics of consumer-resource interactions. The bookconcentrates on host-parasitoid dynamics, but will also be applicable to true predators, herbivores, pathogens and parasites.
	The Effects of Multiple Parasitoid Species on the Gall-Forming Midge, Rhopalomyia californica The cecidomyid midge, Rhopalomyia californica, forms galls only on the shrub, Baccharis pilularis in coastal regions of California. The midge is attacked by a diverse assemblage of parasitoid species. I have found that the midge populations are suppressed to a small fraction of their potential density by the action of the community of parasitoids. I am interested in how the large number of parasitoid species coexist, and what effects the interactions between the parasitoid species have on the abundance and population dynamics of the midge. Current projects on this system include:
	The Effects of Dispersal on the Population Dynamics and Parasitoid Diversity of a Multiparasitoid-Host System funded by NSF grant: DEB-9806635, $294,878, 1998-2002.
	Parasitoid Diversity: Effects of Competition and Seasonality in Host Suppression funded by USDA NRICGP grant: 98-35302-6880 $165,000, 1998-2001.
	The Effects of Host-Plant Genotype and Condition on the Dynamics of a Gall-Forming Midge and its Parasitoids