As natural populations continue to decline globally, direct forms of intervention are increasingly necessary to prevent extinction. One type of intervention, known as demographic rescue, occurs when individuals are added directly to a population to increase abundance and ultimately prevent population extinction. However, the role of infectious disease in demographic rescue remains unknown. To examine the effects of pathogens on demographic rescue, we used a host–pathogen system with the aquatic crustacean Daphnia dentifera as the host and the fungus Metschnikowia bicuspidata as the pathogen. We constructed a randomized 3 × 2 factorial experiment with three rescue treatments (none, low, high) and two pathogen treatments (unexposed, exposed), where the pathogen was introduced via infected individuals during rescue events. We found that adding more individuals to demographically depressed populations increased abundance over the short term; highly supplemented populations initially had 62% more individuals than populations that had no introduced individuals. However, by the end of the experiment, populations that did not have any individuals introduced averaged 640% higher abundance than populations where infected individuals had been added. Thus, the introduction of infected individuals can result in worse demographic outcomes for populations than if no rescue is attempted.

中文翻译：

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当病原体存在时，人口拯救就会步履蹒跚


随着全球自然种群的持续下降，越来越需要直接的干预形式来防止灭绝。一种称为人口拯救的干预措施发生在将个体直接添加到种群中以增加丰度并最终防止种群灭绝时。然而，传染病在人口拯救中的作用仍然未知。为了研究病原体对种群拯救的影响，我们使用了宿主-病原体系统，以水生甲壳类水蚤 Daphnia dentifera 为宿主，真菌 Metschnikowia bicuspidata 为病原体。我们构建了一个随机的 3 × 2 析因实验，其中包含三种救援处理 （无、低、高） 和两种病原体处理 （未暴露、暴露），其中病原体是在救援事件期间通过感染个体引入的。我们发现，在人口统计学上萧条的人口中增加更多的个体会在短期内增加丰度;高度补充的种群最初的个体数比没有引入个体的种群多 62%。然而，到实验结束时，没有引入任何个体的种群比添加感染个体的种群平均丰度高 640%。因此，与不尝试救援相比，感染个体的引入可能会给人群带来更糟糕的人口统计结果。