Ingvarsson PK, Lundberg S
The Effect of a Vector-Borne Disease on the Dynamics of Natural Plant-Populations - a Model for Ustilago-Violacea Infection of Lychnis-Viscaria
Journal of Ecology: 1993 81:263-270
1. A mathematical model was used to study how a parasitic castrating fungus affects the population dynamics of its host plant. The model is based on the interactions between the smut fungus Ustilago violacea and its host plant Lychnis viscaria. The model also includes the pollination process as this plays a central role in the transmission of the fungal spores between plants. 2. Analysis of the model, with the disease absent, revealed that the pollinators have a limiting effect on the growth rate of the population. The model did not include any other density-dependent processes. 3. A condition was calculated which had to be satisfied to enable the disease to invade the host population and it is shown that the disease must possess a minimum transmission potential to be able to invade the host population. The condition was entirely dependent on the demographic processes of the host plant. The higher the recruitment rate of the host, the easier it is for the pathogen successfully to invade the host population. 4. When the disease was able to invade the host population, the disease incidence varied with the transmission potential of the fungal spores. If the disease incidence rose above c. 50%, the host population was driven to local extinction. This was mainly because, at high disease incidence levels, the fraction of pollinators that carried pollen was almost non-existent. This lead to the transmission of the disease to all plants in the population and thus to the extinction of the entire host population.
e-link to journal