Department of Biological Sciences, Simon Fraser University, Burnaby, British Columbia, Canada.
Biodiversity Centre, University of British Columbia, Vancouver, British Columbia, Canada.
Ecology. 2023 Oct;104(10):e4159. doi: 10.1002/ecy.4159. Epub 2023 Sep 13.
Understanding how climate warming will influence species interactions is a key question in ecology and predicting changes in the prevalence of disease outbreaks is particularly challenging. Ectotherms are likely to be more influenced by climatic changes as temperature governs their growth, feeding, development, and behavior. We test the hypothesis that pathogen transmission and host mortality will increase at warmer temperatures using a cyclic forest insect, the western tent caterpillar (WTC), Malacosoma californicum pluviale, and its baculovirus. The virus causes population declines at peak host density. WTC are gregarious and clustering is predicted to increase the risk of within family infection; however, how temperature influences this has not been examined. We investigated the impact of temperature on different components of the transmission process in order to pinpoint the possible mechanisms involved. In the laboratory, leaf consumption increased linearly with rising temperature between 15 and 30°C. Insects died more rapidly from virus infection as temperature increased, but this did not translate into differences in the production of viral transmission stages. To examine the influence of temperature on virus transmission, we created a temperature difference between two greenhouses containing potted red alder trees, Alnus rubra. The cooler greenhouse (mean 19.5°C) was roughly similar to ambient temperatures in the field, while the warmer greenhouse was 10°C higher (mean 29°C). As predicted, both larval movement and feeding were higher at the warmer temperature, while the likelihood of the preinfected, inoculum larvae dying on the tents was twice as high in the cooler greenhouse. This resulted in increased virus mortality and a higher transmission parameter under cooler conditions. Therefore, we suggest that, contrary to our prediction, the reduced movement of infected larvae at colder temperatures increased the risk of infection in these gregarious insects and had a greater impact on virus transmission than the increased activity of the susceptible larvae in warmer conditions. Long-term population data from the field, however, show no relationship between temperature and infection levels, suggesting that local changes in virus transmission might not scale up to population infection levels.
了解气候变暖将如何影响物种相互作用是生态学中的一个关键问题，预测疾病爆发的流行率变化尤其具有挑战性。变温动物（ectotherms）可能更容易受到气候变化的影响，因为温度控制着它们的生长、进食、发育和行为。我们使用一种周期性的森林昆虫——西部天幕毛虫（Malacosoma californicum pluviale）及其杆状病毒来检验温度升高会导致病原体传播和宿主死亡率增加的假设。这种病毒会导致宿主密度高峰期的种群数量下降。西部天幕毛虫是群居的，聚集在一起会增加家族内感染的风险；然而，温度如何影响这一点尚未得到检验。我们研究了温度对不同传播过程的影响，以确定可能涉及的机制。在实验室中，叶片消耗随温度在 15 至 30°C 之间呈线性增加。随着温度升高，昆虫因病毒感染而死亡的速度加快，但这并没有转化为病毒传播阶段产生的差异。为了研究温度对病毒传播的影响，我们在两个包含盆栽红桤木（Alnus rubra）的温室中创造了一个温度差异。较冷的温室（平均 19.5°C）大致类似于野外的环境温度，而较暖的温室温度高出 10°C（平均 29°C）。正如预测的那样，温暖的温度下幼虫的移动和进食都更高，而在较冷的温室中，预先感染的接种幼虫在帐篷上死亡的可能性是在较暖温室中的两倍。这导致了病毒死亡率的增加和较冷条件下更高的传播参数。因此，我们认为，与我们的预测相反，在较冷的温度下，感染幼虫的运动减少增加了这些群居昆虫感染的风险，并且对病毒传播的影响大于在较温暖条件下易感幼虫的活动增加的影响。然而，来自野外的长期种群数据显示，温度与感染水平之间没有关系，这表明病毒传播的局部变化可能不会扩大到种群感染水平。
