Hunt Vicky L, Zhong Weihao, McClure Colin D, Mlynski David T, Duxbury Elizabeth M L, Keith Charnley A, Priest Nicholas K
Milner Centre for Evolution and Department of Biology and Biochemistry, University of Bath, Claverton Down, Bath, BA2 7AY, UK.
J Anim Ecol. 2016 Jan;85(1):178-86. doi: 10.1111/1365-2656.12438. Epub 2015 Oct 16.
Animals must tailor their life-history strategies to suit the prevailing conditions and respond to hazards in the environment. Animals with lethal infections are faced with a difficult choice: to allocate more resources to reproduction and suffer higher mortality or to reduce reproduction with the expectation of enhanced immunity and late-age reproduction. However, the strategies employed to mediate shifts in life-history traits are largely unknown. Here, we investigate the temperature preference of the fruit fly, Drosophila melanogaster, during infection with the fungal pathogen, Metarhizium robertsii, and the consequence of temperature preference on life-history traits. We have measured the temperature preference of fruit flies under different pathogen conditions. We conducted multiple fitness assays of the host and the pathogen under different thermal conditions. From these data, we estimated standard measures of fitness and used age-specific methodologies to test for the fitness trade-offs that are thought to underlie differences in life-history strategy. We found that fungus-infected fruit flies seek out cooler temperatures, which facilitates an adaptive shift in their life-history strategy. The colder temperatures preferred by infected animals were detrimental to the pathogen because it increased resistance to infection. But, it did not provide net benefits that were specific to infected animals, as cooler temperatures increased lifetime reproductive success and survival whether or not the animals were infected. Instead, we find that cold-seeking benefits infected animals by increasing their late-age reproductive output, at a cost to their early-age reproductive output. In contrast, naive control flies prefer warmer temperatures that optimize early-age reproductive, at a cost to reproductive output at late ages. These findings show that infected animals exhibit fundamentally different reproductive strategies than their healthy counterparts. Temperature preference can facilitate shifts in strategy, but not without inevitable trade-offs.
动物必须调整其生活史策略以适应当前环境条件，并应对环境中的危险。感染致命疾病的动物面临着艰难的抉择：是分配更多资源用于繁殖并承受更高的死亡率，还是减少繁殖以期增强免疫力并在晚年繁殖。然而，用于调节生活史特征转变的策略在很大程度上尚不清楚。在此，我们研究了果蝇（Drosophila melanogaster）在感染真菌病原体罗伯茨绿僵菌（Metarhizium robertsii）期间的温度偏好，以及温度偏好对生活史特征的影响。我们测量了不同病原体条件下果蝇的温度偏好。我们在不同热条件下对宿主和病原体进行了多次适合度测定。根据这些数据，我们估计了适合度的标准指标，并使用特定年龄的方法来测试被认为是生活史策略差异基础的适合度权衡。我们发现，感染真菌的果蝇会寻找更凉爽的温度，这有助于其生活史策略发生适应性转变。被感染动物偏好的较低温度对病原体不利，因为这会增加对感染的抵抗力。但是，这并没有为被感染动物带来特定的净益处，因为无论动物是否被感染，较低温度都会增加其一生的繁殖成功率和存活率。相反，我们发现，寻找低温通过增加被感染动物晚年的繁殖产量而使其受益，但代价是其早期的繁殖产量。相比之下，未感染的对照果蝇更喜欢温暖的温度，这会优化其早期繁殖，但以晚年的繁殖产量为代价。这些发现表明，被感染的动物与健康动物表现出根本不同的繁殖策略。温度偏好可以促进策略转变，但不可避免地会有权衡。
