PARENT SESSION
Oral Session # 48: Mutualism - Parasitism I: Plants; Modeling.
Presiding: K Jayachandran
Wednesday, August 6. 8:00 AM to 11:30 AM, SITCC Meeting Room 203.
Ecological conditions that favor the evolution of reduced virulence in environmentally transmitted symbiotic parasites.
Golinski, Michael*,1, 1 New Mexico State University, Las Cruces, NM, United States
ABSTRACT- Mathematical models that explore the evolution of reduced virulence in environmentally transmitted parasites within the framework of the intermediate-virulence hypothesis are non-existent in the theoretical literature. For this reason, we develop a population-dynamic model for exploring ecological conditions that favor evolution towards reduced virulence in environmentally transmitted symbiotic parasites that infect an isolated population of susceptible hosts. First, we introduce a non-linear tradeoff function based on Michaelis-Menten enzyme kinetics, in which the level of parasite virulence is determined by the number of uninfected hosts (substrate concentration), the number of free-living parasites (enzyme concentration), and the rate of environmental transmission. Given the tradeoff, we specify the basic reproductive rate of the parasite, and show the analytical conditions necessary for an isolated population of susceptible hosts to be invaded by a population of free-living parasites. For parasite invasion, we derive an equation that measures the rate of spread of infected hosts, and show the explicit solution for the level of environmental transmission that optimizes the rate of infection of susceptible hosts by free-living parasites. Our results show that for an isolated population of susceptible hosts, selection will favor near-intermediate levels of virulence in environmentally transmitted parasites.
Key words: Parasite, Environmental transmission, Intermediate-virulence hypothesis, Michaelis-Menten enzyme kinetics