The effect of parasites on host population density and extinction:: Experimental epidemiology with Daphnia and six microparasites
The effect of parasites on host population density and extinction:: Experimental epidemiology with Daphnia and six microparasites
复制标题
DOI：
10.1086/303404
复制
发表时间：
2000-11-01
影响因子：
2.9
通讯作者：
Mangin, KL
中科院分区：
文献类型：
--
作者：
Ebert, D;Lipsitch, M;Mangin, KL
在某些情况下，寄生虫会降低宿主密度并导致宿主种群灭绝，但在其他情况下则不会。流行病学模型表明，寄生虫对个体宿主的可变影响可以解释这种群体水平上的变异性。在这里，我们的目标是支持这一假设与一个特定的流行病学模型，使用跨寄生虫物种的方法。我们比较了六种寄生虫对宿主繁殖力和存活率的影响，以及它们对克隆宿主种群密度和灭绝风险的影响。我们对比我们的经验结果的人口密度从确定性模型的预测和对比我们的经验结果的主机和寄生虫灭绝率与随机模型预测。使用了五种水平传播的微寄生虫（两种细菌：白色细菌病，多枝巴氏杆菌;两种微孢子虫：Glugoides nervosa，Ordospora colligata;一种真菌：Metschnikowiella biscuspidata）;和六种垂直传播的大型甲壳动物Daphnia magna的微孢子虫（Flabelliforma magnivora）。在生命表实验中，我们量化了个体寄生和健康宿主的繁殖力和存活率，并将其与寄生虫对宿主种群密度的影响和微观种群中宿主种群灭绝的可能性进行了比较。寄生虫种类在其对宿主生殖力、宿主存活率、宿主密度降低以及它们使宿主种群灭绝的频率的影响上变化很大。受感染的宿主产生的后代越少，受感染的宿主种群的密度就越低。对于垂直传播的寄生虫株，这种对宿主密度的影响比水平传播的寄生虫相对更强。正如随机模拟所预测的那样，寄生虫对个体宿主生存和繁殖力的强烈影响增加了宿主种群灭绝的风险。寄生虫的排泄也是如此。我们的研究结果对微寄生虫在生物防治计划中的应用以及寄生虫在推动小种群灭绝中的作用具有影响。
Parasites have been shown to reduce host density and to induce host population extinction in some cases but not in others. Epidemiological models suggest that variable effects of parasites on individual hosts can explain this variability on the population level. Here, we aim to support this hypothesis with a specific epidemiological model using a cross-parasite species approach. We compared the effect of six parasites on host fecundity and survival to their effects on density and risk of extinction of clonal host populations. We contrast our empirical results of population density with predictions from a deterministic model and contrast our empirical results of host and parasite extinction rates with those predicted by a stochastic model. Five horizontally transmitted microparasites (two bacteria: white bacterial disease, Pasteuria ramosa; two microsporidia: Glugoides intestinalis, Ordospora colligata; one fungus: Metschnikowiella biscuspidata); and six strains of a vertically transmitted microsporidium (Flabelliforma magnivora) of the planktonic crustacean Daphnia magna were used. In life table experiments, we quantified fecundity and survival in individual parasitized and healthy hosts and compared these with the effect of the parasites on host population density and on the likelihood of host population extinction in microcosm populations. Parasite species varied strongly in their effects on host fecundity, host survival, host density reduction, and the frequency with which they drove host populations to extinction. The fewer offspring an infected host produced, the lower the density of an infected host population. This effect on host density was relatively stronger for the vertically transmitted parasite strains than for the horizontally transmitted parasites. As predicted by the stochastic simulations, strong effects of a parasite on individual host survival and fecundity increased the risk of host population extinction. The same was true for parasite extinctions. Our results have implications for the use of microparasites in biological control programs and for the role parasites play in driving small populations to extinction.