Collaborative Research: Experimental Tests of the Adaptive Significance of Ectotherm Thermoregulation

合作研究：变温体温调节适应性意义的实验测试

• 批准号: 0416205
• 负责人: Patrick Phillips
• 金额: $ 36.73万
• 依托单位: University of Oregon Eugene
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-06-01 至 2008-05-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0416205&HistoricalAwards=false
• 关键词: Collaborative; Research; Experimental; Tests; Adaptive

The body temperature of an animal has profound influence on all aspects of its biology. Extreme temperatures can be damaging physiologically or even lethal, but even intermediate body temperatures determine rates of physiological activities and of reproductive output. Endothermal animals (mainly birds and mammals) control their body temperatures by adjusting physiology (for example, metabolic heat production, perspiration); but ectothermal animals (e.g., nematodes, insects, fishes, reptiles) are generally unable to do this. Nevertheless, ectotherms can instead adjust their behavior (for example, amount of time spent in sun versus shade) to gain remarkable control over body temperature: many carefully regulate their body temperature at narrow levels ("thermal preferences") that vary from species to species. Such thermal preferences of species often correlate with temperatures that maximize physiological performance (sprint speed, digestive efficiency, sensory acuity), and accordingly a classical hypothesis proposes that thermal preferences of ectotherms will have evolved to match temperatures that maximize rates of population growth ("fitness"). This adaptive hypothesis is widely accepted and is fundamental to physiological ecology, but yet has never been tested directly.This proposal provides a rigorous exploration of the biological consequences of thermal preferences of ectotherms. Specifically, it develops an integrated set of experimental, theoretical, and comparative studies focusing on two species [fruitfly (Drosophila melanogaster), soil nematode (Caenorhabditis elegans)] that serve as general models for economically and ecologically important animal groups (insects and nematodes). The project exploits powerful new methods (developed by neurobiologists) of experimentally manipulating thermal preferences. Thermoregulatory precision of both animals will be manipulated both surgically and via mutation, and thermal preferences themselves will be shifted via artificial selection (selective breeding). Then the resultant impacts on fitness will be measured. If the classical hypothesis holds, then (for example) individuals with shifted thermoregulatory set-points will have reduced fitness in a thermal gradient relative to their fitness at a fixed temperature, whereas control individuals will show similar fitness in both environments. The project also completes a novel theoretical model of thermal preferences. The preliminary model shows that optimal set-points in fluctuating environments are actually lower than the temperature maximizing fitness in a constant environment. Comparative data on insects and lizards will be used to challenge the model's predictions.These studies have considerable applied relevance. Establishing whether and how thermal preferences actually maximize rates of population growth will have crucial implications not only for those studying the effects of the thermal environment on population growth of arthropod and nematode pests or disease vectors, but also for applied entomologists needing to determine cost-effective estimates of optimal temperature for mass rearing of bio-control agents.

动物的体温对其生物学的各个方面都有深远的影响。极端温度可能对生理造成损害，甚至是致命的，但即使是中等体温也决定了生理活动和生殖产出的速度。恒温动物（主要是鸟类和哺乳动物）通过调节生理机能（如代谢产热、排汗）来控制体温；但异温动物（如线虫、昆虫、鱼类、爬行动物）通常无法做到这一点。然而，变温动物可以调整自己的行为（例如，在阳光下和阴凉处呆的时间）来获得对体温的显著控制：许多动物小心翼翼地将体温调节在一个狭窄的水平上（“热偏好”），这个水平因物种而异。物种的这种热偏好通常与生理性能（冲刺速度、消化效率、感官敏锐度）最大化的温度相关，因此一个经典假设提出，变温动物的热偏好将进化到与种群增长率最大化的温度相匹配（“适应性”）。这种适应性假说被广泛接受，是生理生态学的基础，但从未被直接验证过。这一建议提供了一个严格的探索变温动物的热偏好的生物学后果。具体来说，它发展了一套完整的实验、理论和比较研究，重点是两个物种[果蝇（Drosophila melanogaster），土壤线虫（Caenorhabditis elegans）]，作为经济上和生态上重要的动物类群（昆虫和线虫）的一般模型。该项目利用强大的新方法（由神经生物学家开发），通过实验操纵热偏好。这两种动物的温度调节精度将通过手术和突变来控制，热偏好本身将通过人工选择（选择性育种）来改变。然后测量结果对适应度的影响。如果经典假设成立，那么（例如）温度调节设定点改变的个体在温度梯度下的适合度相对于在固定温度下的适合度会降低，而对照个体在两种环境下的适合度都相似。该项目还完成了一个新的热偏好理论模型。初步模型表明，波动环境下的最优设定点实际上低于恒定环境下的温度最大化适应度。昆虫和蜥蜴的比较数据将被用来挑战模型的预测。这些研究具有相当大的应用意义。确定热偏好是否以及如何使种群增长率最大化，不仅对研究热环境对节肢动物和线虫害虫或病媒种群增长的影响具有重要意义，而且对需要确定大规模饲养生物防治剂的最佳温度的成本效益估计的应用昆虫学家也具有重要意义。