THEORETICAL AND EMPIRICAL-STUDIES OF METAPOPULATIONS - POPULATION ANDGENETIC DYNAMICS OF THE SILENE-USFILAGO SYSTEM

Host-pathogen population dynamics may often only be understood by a mu ltifaceted approach designed to understand processes at a regional as well as local scale. We have investigated the regional population dyna mics of the anther-smut Ustilago violacea, a pollinator-transmitted fu ngal disease, and its plant host Silene alba, using descriptive, exper imental, and theoretical approaches. A 7-year survey of multiple natur al populations revealed persistence of host and pathogen despite a hig h rate of population turnover. In an experimental metapopulation, dise ase spread was greater and more rapid in populations that were relativ ely isolated or had a previous history of disease occurrence. A comput er simulation showed that spatial substructuring can drastically alter expectations based on analytical results from single population model s of host-pathogen systems. Moreover, the simulation reproduced many o f the patterns detected in the long-term survey and predicted that hea lthy populations should be more resistant than diseased ones, as found experimentally.