Joint effects of global change and biological invasions on insect-vectored generalist pathogens.


Research Objectives

  • Develop general mathematical theory to examine the joint effects of host community structure and resource supply to the hosts on generalist vector-transmitted pathogens.
  • Parameterize the models we develop with data on native and introduced grasses in Pacific grasslands to predict effects of global change on disease dynamics.
  • Test the model predictions using field experiments in north-central California and Corvallis Oregon.

Study Species

  • Avena fatua (Wild Oats)
  • Bromus carinatus (California Brome)
  • Bromus hordeaceus (Soft Brome)
  • Elymus glaucus (Blue Wildrye)
  • Hordeum marinum (Seaside Barley)
  • Koeleria macrantha (Prairie Junegrass)

Collaborators

 

The pacific coastal grasslands are classic examples of biological invasions. The native perennial grasses have been almost completely displaced by introduced annual grasses, visible in the foreground.

I am collaborating with a group of six theoreticians and grassland ecologists to predict the effects of environmental change and host diversity on the dynamics of insect-vectored generalist pathogens. We are developing mathematical theory of generalist vector-transmitted pathogens that explicitly incorporates host competition for abiotic resources. We will test the predictions of this theory using geographic-scale field experiments in Mediterranean-type grasslands with an aphid-vectored plant virus, barley yellow dwarf (BYDV). The experimental sites are on a precipitation gradient. By performing nitrogen addition and manipulating host community structure, we will test how changes in moisture and nitrogen availability interact with changes in host community diversity and composition to control disease dynamics. We are specifically interested in the changes in the host community driven by the historical replacement of native perennial grasses by introduced annuals. We hypothesize that annual and perennial grasses may have complementary effects on pathogen persistence in the system. The BYDV system allows us to create spatially- and phylogenetically-replicated experimental communities that mimic five important types of disease systems. Our ultimate goal is to develop a general theoretical framework to predict the effects of human activities on a variety of host communities and pathogens. This project is funded by the NSF Ecology of Infectious Disease program through 2010.