The regulation of host population growth by parasitic species.

摘要: The nature of parasitism at the population level is defined in terms parasite's influence on natural intrinsic growth rate its host population. It suggested that this related to average parasite burden/host and hence statistical distribution parasites within population.Theoretical models host–parasite associations are used assess regulatory parasitic species growth. Model predictions suggest three specific groups processes particular importance: over-dispersion numbers/host, density dependence mortality or reproduction parasite-induced increases faster than linearly with burden. Other mechanisms shown have a destabilizing influence, namely: reduction reproductive potential, direct time delays development transmission stages parasite.These be commonly observed features host-parasite associations. argued interactions real world characterized by degree tension between these forces parameter values life-cycles very far from being haphazard selection all numerically possible values. evolutionary pressures will tend counteract strong force an equally influence. Empirical evidence support suggestion in, for example, larval digeneans molluscan hosts (parasite-induced potential counteracted tight density-dependent constraints growth), protozoan mammalian (direct well-developed immunological response host).The type laboratory field data required improve our understanding dynamical properties discussed it quantitative measurement rates mortality, degrees over-dispersion, both would provide important first step. value work area demonstrated reference studies which highlight