PARENT SESSION
Organized Oral Session 3: Plant Pathogens in Nature: Rethinking Vegetation Dynamics
Organized by: CM Malmstrom and A Power
Wednesday, August 6. 8:00 AM to 11:30 AM, SITCC Meeting Room 205.

Changes in host life history and population dynamics due to pathogen epidemics.

Jarosz, Andrew^*,1, ¹ Michigan State University, East Lansing, MI, USA

ABSTRACT- Pathogen infections are well known for their effects on fitness, which can ultimately alter life history of the host. These pathogen-induced changes can have cascading effects by influencing population structure and growth. My lab has been investigating the population level consequences of epidemics in two systems. Our work on Jack-in-the-pulpit indicates that infection by the systemic rust, Uromyces ari-triphylli, reduces survivorship and growth. Infected plants also change their pattern of reproduction by displaying an increased propensity to produce flowers, while reducing the number of asexually produced cormlets. At the population level this results in altered size structure within populations and reduced population growth rates. This decrease in growth rates seems to be exacerbating a trend in population decline that may be due to habitat fragmentation. We are also investigating how changes in virulence in the chestnut pathogen Cryphonectria parasitica influence populations of American chestnut. Virulence is altered by the presence of a double-stranded (ds) RNA hyperparasite that infects the pathogen intra-cellularly. Reduced virulence in C. parasitica does not always change population dynamics. Size structure and growth rates of the chestnut population are determined ultimately by subtle changes in growth and survivorship of sub-adult plants.

Key words: demography, flowering phenology, Pathogen virulence, Lefkovitch matrices