Simulation of population dynamics of the parasite Haematoloechus coloradensis in its three host species: effects of environmental temperature and precipitation

We describe the development and evaluation of a simulation model representing the life cycle of the parasite Haematoloechus coloradensis, and use this model to examine effects of variation in temperature and precipitation on parasite population dynamics. The model consists of four submodels representing: (1) dynamics of parasite eggs in the environment; and infection, parasite development within, and resulting population dynamics of (2) snail, (3) odonate, and (4) frog hosts. Simulated population dynamics and seasonal variation in prevalences of infection for second and definitive hosts generally agreed with field observations. Differences between simulated and observed variation in prevalence for the first intermediate host probably were due to failure of the model to represent effects of temperature on parasite development within snails and parasite-induced host mortality. High precipitation and short summers (favorable conditions for host populations) did not show important effects on prevalences for the three host species in the long term. Simulated effects of low precipitation and extended summers (unfavorable conditions for host species) indicated that temperature had a greater impact on parasite population dynamics than precipitation. Susceptible host abundance was decreased during extended summers to levels below which encounter rate could maintain the parasite population. Overall, results suggest that timing of occurrence of a given disturbance may be as important in determining impact on parasite population dynamics as the specific nature of the disturbance. (C) 1998 Elsevier Science B.V.