Evolution of senescence in plants

衰老，俗称“老龄化”，是指个体逐渐退化，导致老年存活率和繁殖率下降。衰老在各种生物中极为普遍，包括人类、其他动物、植物，甚至真菌和细菌。理论预测，除了与年龄相关的存活率和繁殖率下降外，我们还应该预料到后代质量的下降。然而，大多数关于衰老的研究忽略了这些父母年龄的影响，隐含地假设所有的后代都具有相同的质量。这表明，目前的方法低估了进化上偏爱的衰老速度，为创新研究提供了机会。我的研究计划的长期目标是开发和测试衰老的进化理论，重点是父母年龄的影响。我的团队将理论、实地和实验室工作相结合，并使用浮萍属水生植物作为模型系统。四个主要目标支持我的长期目标：1.测试年迈父母的子女是否比年轻父母的子女更不能承受压力。实验将集中在三个重要的压力源上：盐度、高温和pH。我们将确定高龄父母是否会加剧压力对后代的负面影响。2.测试野生植物是否存在亲本年龄效应。植物将在池塘中使用浮动平台种植，以确定在实验室中观察到的父母年龄效应是否也在自然界中发生，或者它们是否仅仅是良性实验室条件的结果。3.检验父母年龄效应是否会改变人口增长。我们将开发经典人口增长模型的扩展，以纳入父母年龄的影响。然后，我们将测试在人口增长模型中包括父母年龄效应是否会提高他们的预测能力。4.检验亲本年龄效应是否在全无性系水平上发生。由于Lemna是克隆繁殖的，以前的研究集中在生理个体水平上的衰老。我们将操纵整个克隆的有效年龄(使用温度处理来改变克隆世代的数量)，以测试较年长的克隆产生的后代是否比较年轻的克隆产生的适合度较低。衰老是生态学和进化论的中心话题。我正在进行的研究表明，有必要考虑父母年龄的影响，以了解衰老的演变。这项拟议的工作建立在此基础上，将父母年龄效应与应激生物学、生殖模式和人口增长等不同主题联系起来。我的研究项目带来的发现将对人口学家、进化生物学家和生态学家有价值。由于我统一的概念重点，我的研究将与理解衰老的一般相关，而不仅仅是植物。此外，这项研究将有助于促进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, known colloquially as `aging', is the progressive deterioration of individuals leading to decreased rates of survival and reproduction in old age. Senescence is extremely common in diverse organisms including humans, other animals, plants, and even fungi and bacteria. Theory predicts that in addition to age-related declines in survival and reproduction, we should also expect declines in offspring quality. Yet most work on senescence ignores these parental age effects, implicitly assuming that all offspring are of equal quality. This suggests that current approaches underestimate evolutionarily favoured rates of senescence, providing opportunities for innovative research. The long-term goal of my research program is to develop and test evolutionary theories of senescence with a focus on parental age effects. My team combines theory, field, and lab work, and uses floating aquatic plants in the genus Lemna as a model system. Four major objectives support my long-term goal: 1. Test whether offspring of old parents are less stress tolerant than those of young parents. Experiments will focus on three important stressors: salinity, high temperatures, and pH. We will determine whether advanced parental age exacerbates negative effects of stress on offspring. 2. Test whether parental age effects occur in wild plants. Plants will be grown in ponds using floating platforms to determine whether parental age effects observed in the lab also occur in nature, or if they are simply a result of benign lab conditions. 3. Test whether parental age effects alter population growth. We will develop extensions of classic population growth models to incorporate parental age effects. We will then test whether including parental age effects in population growth models improves their predictive power. 4. Test whether parental age effects occur at the whole-clone level. As Lemna is clonally reproducing, prior studies have focused on senescence at the level of physiological individuals. We will manipulate the `effective age' of whole clones (using temperature treatments to vary the number of clonal generations) to test whether older clones produce lower-fitness offspring than younger ones. Senescence is a central topic in ecology and evolution. My ongoing research demonstrates the necessity of considering parental age effects to understand the evolution of senescence. The proposed work builds on this foundation by linking parental age effects to diverse topics such as stress biology, modes of reproduction, and population growth. The discoveries delivered by my research program will be valuable to demographers, evolutionary biologists, and ecologists. Due to my unified conceptual focus, my research will be relevant to understanding senescence in general, not just in plants. Additionally, 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.