Population Dynamics and the Evolution of Virulence in Epidemiological Models with Discrete Host Generations

✍ Scribed by Jacob C. Koella; Michael Doebeli

• Publisher: Elsevier Science
• Year: 1999
• Tongue: English
• Weight: 296 KB
• Volume: 198
• Category: Article
• ISSN: 0022-5193
• DOI: 10.1006/jtbi.1999.0925

✦ Synopsis

Chaos is the likely outcome of the interaction between a parasite and a host with discrete generations, if the parasite's virulence is high and if transmission from one generation to the next is held constant. We studied two alternative routes of transmission-vertical transmission from infecteds to their offspring, and transmission via long-lasting spores produced in those individuals that were killed by the infection-to investigate the influence of the transmission route on the system's evolution and population dynamics. The major results are: (1) vertical transmission often leads to low virulence, thus confirming most epidemiological models. However, if hosts can become super-infected, the evolutionary dynamics of virulence can have several equilibrium points, including 100% disease-induced mortality; (2) when parasites are transmitted with long-lasting spores, the evolutionary dynamics of virulence can become unstable, leading to the repeated bifurcation of two sub-populations with high and low virulence or to punctuated equilibria with sudden changes in the average level of virulence; (3) in general, the evolution of virulence moves the system to an area where the population dynamics are stable. When evolution leads to chaos, the system most often becomes extinct. Only for a restricted parameter space in the system where transmission from one generation to the next is via long-lasting spores do the dynamics become chaotic without extinction of the system. Copyright 1999 Academic Press.