Host density has limited effects on pathogen invasion, disease‐induced declines and within‐host infection dynamics across a landscape of disease
Host density has limited effects on pathogen invasion, disease‐induced declines and within‐host infection dynamics across a landscape of disease
复制标题
宿主密度对病原体入侵、疾病引起的衰退以及整个疾病领域的宿主内感染动态的影响有限
DOI：
10.1111/1365-2656.13823
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发表时间：
2022
影响因子：
4.8
通讯作者：
Briggs, Cheryl J.
中科院分区：
文献类型：
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作者：
Wilber, Mark Q.;Knapp, Roland A.;Smith, Thomas C.;Briggs, Cheryl J.
1.假设宿主密度是病原体入侵后野生动物种群的反应和结果变化的主要驱动因素。虽然宿主密度对病原体传播的影响已被广泛研究，但这些研究主要是理论分析和小规模实验。这种关注导致了关于宿主密度如何驱动在该领域观察到的疾病结果的变异性的不完整的图片。在这里，我们利用了数百个复制两栖动物种群的数据集，这些种群在宿主密度上有数量级的差异。我们使用这些数据来测试宿主密度对两栖动物杀死真菌病原菌Batrachochytrium dendrobaidae（Bd）到达后三个结果的影响：Bd成功入侵宿主种群并导致病原体爆发的概率，爆发后宿主种群水平下降的幅度以及驱动两栖动物病原体系统中种群水平结果的宿主内感染动态。根据以前的小规模传播实验，我们预计密度较高的人群更有可能经历Bd爆发，并在爆发后遭受更大比例的下降。为了检验这些预测，我们开发并拟合了一个隐马尔可夫模型，该模型解释了我们调查的两栖动物种群中观察不到的疾病爆发状态。与我们的预测相反，我们发现宿主密度对成功入侵的可能性、入侵后种群下降的幅度和宿主内感染强度的动态的影响很小。环境条件，如夏季温度，冬季的严重程度和病原体水库的存在，更能预测疾病结果的变异性。我们的研究结果强调了从小规模传播实验中推断结果的局限性，并提供了强有力的证据，表明宿主密度的变化并不一定会导致病原体到达后宿主种群反应的变化。在应用背景下，我们表明，宿主密度和疾病之间的反馈不一定会影响两栖动物Bdsystems的保护问题的再引入工作的成功。
1. Host density is hypothesized to be a major driver of variability in the responses and outcomes of wildlife populations following pathogen invasion. While the effects of host density on pathogen transmission have been extensively studied, these studies are dominated by theoretical analyses and small‐scale experiments. This focus leads to an incomplete picture regarding how host density drives observed variability in disease outcomes in the field.2. Here, we leveraged a dataset of hundreds of replicate amphibian populations that varied by orders of magnitude in host density. We used these data to test the effects of host density on three outcomes following the arrival of the amphibian‐killing fungal pathogenBatrachochytrium dendrobatidis(Bd): the probability thatBdsuccessfully invaded a host population and led to a pathogen outbreak, the magnitude of the host population‐level decline following an outbreak and within‐host infection dynamics that drive population‐level outcomes in amphibian–pathogen systems.3. Based on previous small‐scale transmission experiments, we expected that populations with higher densities would be more likely to experienceBdoutbreaks and would suffer larger proportional declines following outbreaks. To test these predictions, we developed and fitted a Hidden Markov Model that accounted for imperfectly observed disease outbreak states in the amphibian populations we surveyed.4. Contrary to our predictions, we found minimal effects of host density on the probability of successfulBdinvasion, the magnitude of population decline followingBdinvasion and the dynamics of within‐host infection intensity. Environmental conditions, such as summer temperature, winter severity and the presence of pathogen reservoirs, were more predictive of variability in disease outcomes.5. Our results highlight the limitations of extrapolating findings from small‐scale transmission experiments to observed disease trajectories in the field and provide strong evidence that variability in host density does not necessarily drive variability in host population responses following pathogen arrival. In an applied context, we show that feedbacks between host density and disease will not necessarily affect the success of reintroduction efforts in amphibian‐Bdsystems of conservation concern.