Evolution of senescence in plants

衰老--随着年龄的增长，身体的退化会导致死亡风险的增加和繁殖率的降低--横跨生命之树，从细菌到复杂的多细胞物种。尽管衰老无处不在，但衰老令人费解，因为在其他条件相同的情况下，自然选择应该比那些衰老的个体更有利于不衰老的个体。这一明显的悖论使衰老成为生物学中一个长期感兴趣的话题，并激发了我研究计划的长期目标：开发和测试衰老的进化理论，重点是植物的衰老。 理想情况下，衰老研究应该纵向跟踪多个世代的种群，这对长寿物种来说是一个困难的目标。因此，我建议研究小浮萍的衰老，这是一种短暂的水生植物，它允许在几周内积累即使在其他短暂的植物(例如一年生植物)中也需要数年才能获得的数据。我和我的学生将在几个方面部署这个模型系统： 1.老龄化的跨代效应。高龄不仅会减少存活和繁殖，还会降低后代的质量；然而，人们对衰老的这第三个组成部分知之甚少。我们对这一现象的研究将对人口学产生重要的见解，不仅对植物，而且对许多被认为经历了后代适应性逐渐侵蚀的物种(例如人类)都有广泛的影响。 2.环境变化和老龄化速度。理论预测，加速生长的条件会导致更快的衰老。例如，在植物中，温度、光照、养分和二氧化碳的可用性是环境属性中的一部分，它们的变化可能会改变衰老速度。我们将通过单独和交互操作这些变量来测试这一点。特别是，二氧化碳和温度与理解气候变化中生活史轨迹的变化有关。 3.衰老的进化延展性。理论预测，在某种意义上，一个种群的衰老速度应该与其成员在其祖先进化的环境条件下的预期寿命相匹配。这表明，从条件持续导致快速生长的池塘收集的浮萍，即使转移到普通条件下，也应该比那些条件导致生长缓慢的池塘衰老得更快。我们将从加拿大西部收集Lemna，并使用现代比较方法来解释种群间的相关性，确定共同花园实验中的衰老速度是否与来源池塘的相关环境数据有关。 随着在进化生物学、种群生态学和水生植物学领域的预期发现，这项研究将有助于推动生物人口学领域的发展并提供培训，生物人口学是一门由于加拿大人口老龄化而日益重要的社会经济学科。

Senescence—bodily deterioration leading to an elevated risk of death and a lower rate of reproduction with advancing age—spans the tree of life, from bacteria to complex multi-cellular species. Despite its ubiquity, senescence is puzzling because all else being equal, natural selection should favour individuals that don't senesce over those that do. This apparent paradox makes senescence a topic of perennial interest in biology and inspires the long-term goal of my research program: to develop and test evolutionary theories of senescence, with an emphasis on aging in plants. Ideally, senescence studies should track populations longitudinally over multiple generations, a difficult goal in long-lived species. Thus, I propose to study senescence in Lemna minor, a short-lived aquatic plant that allows, in weeks, the amassment of data that would take years to acquire even in other short-lived plants (e.g., annuals). My students and I will deploy this model system on several fronts: 1. Trans-generational effects of aging. Advanced age not only reduces survival and reproduction, it can also reduce offspring quality; yet this ‘third component’ of senescence is poorly understood. Our studies of this phenomenon will generate important insights into demography, with broad implications not only for plants, but also for the many species (e.g., humans) thought to experience a progressive erosion of offspring fitness. 2. Environmental variation and rates of aging. Theory predicts that conditions that speed growth lead to faster senescence. For instance, in plants, temperature, light, nutrient and CO2 availability are among environmental attributes whose variation may alter rates of senescence. We will test this by manipulating these variables alone and interactively. In particular, CO2 and temperature are relevant to understanding changes in life-history trajectories in a changing climate. 3. Evolutionary malleability of senescence. Theory predicts that a population’s rate of senescence should, in a sense, match its members’ expected lifespan in the environmental conditions under which their ancestors evolved. This suggests that Lemna collected from ponds whose conditions consistently lead to rapid growth should have faster senescence than those whose conditions lead to slow growth, even when transferred to common conditions. We will collect Lemna from across Western Canada, and, using modern comparative methods to account for inter-population relatedness, determine whether rates of senescence in a common-garden experiment are related to relevant environmental data from the source ponds. Along with anticipated discoveries in the subjects of evolutionary biology, population ecology, and aquatic botany, this research will help advance—and provide training in—the field of biodemography, a discipline of increasing socio-economic importance due to Canada’s aging population.