The Role of Senescence in Life History Evolution

衰老在生命史进化中的作用

• 批准号: 9707473
• 负责人: David Reznick
• 金额: $ 40万
• 依托单位: University of California-Riverside
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 1998
• 资助国家: 美国
• 起止时间: 1998-03-01 至 2003-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=9707473&HistoricalAwards=false
• 关键词: Role; Senescence; Life; History; Evolution

9707473 Reznick Most current research on the aging process evaluates the influence of environmental factors on the rate of aging or characterizes individual genes that influence lifespan in two model organisms, the nematode Caenorhabditis elegans and the fruitfly Drosophila melanogaster. We propose evaluating aging instead from an evolutionary perspective. Senescence is thought to have evolved because the strength of selection declines with an individual's age; natural selection will have the greatest influence on individuals that are early in their reproductive lifespans because they have only begun to contribute offspring to the next generation. The influence of selection declines to zero when individuals are no longer reproducing or caring for offspring. Two genetic mechanisms, mutation accumulation and antagonistic pleiotropy, can account for the evolution of senescence due to this age-specific decline in the strength of selection. Both mechanisms predict that high extrinsic mortality rates will select for earlier senescence. "Extrinsic mortality" refers to death to external causes, such as predation. We will test this prediction by evaluating the lifespan and lifetime reproductive performance of guppies derived from high and low predation environments. In our earlier work, we established that natural populations of guppies from Trinidad experience high versus low mortality rates, correlated with the species of predators present. Guppies from high predation environments mature at an earlier age, smaller size, and devote more of their resources to reproduction than their counterparts from low predation environments. These differences were shown to have a genetic basis. They were further evaluated by modifying mortality rates in natural populations, resulting in the evolution of these same life history patterns over time intervals as short as four years. These combined studies argue that predators and mortality rates have selected for changes in the early life history, or that the differences that we observed among populations in early life history represent an adaptation to prevailing mortality rates. These results provide the rationale for predicting that predation has also influences the evolution of the aging process.! Evaluating aging in these fish potentially provides a new model system for studying the aging process, a new way of identifying genes associated with aging, and a means for answering a question that is not accessible in all lab-based systems considered thus far, which is "why do we see such dramatic differences in lifespan among species in nature?".

目前大多数关于衰老过程的研究都是评估环境因素对衰老速度的影响，或者描述影响两种模式生物（秀丽隐杆线虫和果蝇）寿命的单个基因。我们建议从进化的角度来评估衰老。衰老被认为是进化的结果，因为选择的强度随着个体年龄的增长而下降；自然选择对处于生殖寿命早期的个体影响最大，因为他们才刚刚开始为下一代贡献后代。当个体不再繁殖或照顾后代时，选择的影响降至零。两种遗传机制，突变积累和拮抗多效性，可以解释由于这种年龄特异性选择强度下降而导致的衰老进化。这两种机制都预测高的外在死亡率将选择更早的衰老。“外在死亡”指的是外部原因导致的死亡，比如被捕食。我们将通过评估来自高捕食环境和低捕食环境的孔雀鱼的寿命和终身繁殖性能来验证这一预测。在我们早期的工作中，我们确定了特立尼达的孔雀鱼自然种群的死亡率高与低，与捕食者的种类有关。来自高捕食环境的孔雀鱼比来自低捕食环境的孔雀鱼成熟得更早，体型更小，并且投入更多的资源用于繁殖。这些差异是有遗传基础的。通过改变自然种群的死亡率对它们进行进一步评估，结果是这些相同的生活史模式在短至四年的时间间隔内演变。这些综合研究认为，捕食者和死亡率选择了早期生活史的变化，或者我们在早期生活史中观察到的种群之间的差异代表了对普遍死亡率的适应。这些结果为预测捕食也会影响衰老过程的进化提供了理论依据。评估这些鱼类的衰老可能为研究衰老过程提供一个新的模型系统，一种识别与衰老相关基因的新方法，以及一种回答迄今为止所有基于实验室的系统都无法解决的问题的方法，即“为什么我们看到自然界物种之间的寿命差异如此巨大？”。