Evolutionary adaptation to intensifying drought across a geographic gradient: a comprehensive evaluation of Fisher's Fundamental Theorem

该项目将通过调查一种原产于加州的野生开花植物--通常被称为婴儿蓝眼睛--对干旱加剧的适应速度，来检验长期存在的进化理论，即种群如何快速适应不断变化的环境。种群适应应激环境条件的能力取决于生存和繁殖过程中是否存在遗传变异，以及影响生存和繁殖的性状的遗传变异，如植物生理和繁殖时机。很少有研究衡量适应过程，以确定决定植物种群在自然界中适应有限水分条件的速度的因素。这项研究将综合以下措施：(1)植物生存和繁殖的遗传变异，包括自然种群内和自然种群之间的遗传变异，以及有助于植物表现的性状的遗传变异；(2)野生种群的自然选择；(3)基于遗传的生存和繁殖方面的世代变化。基于进化理论的统计模型将被用来预测每个研究群体中应该发生的适应性变化的幅度。这些预测将与两代人之间观察到的存活率和繁殖率的实际变化进行比较。将通过美国生态学会、美国印第安人科学与工程学会和奇卡诺和美洲原住民科学促进会招募代表人数不足的本科生参加这项研究。这些学生将接受从田间和育种实验中收集的遗传数据的设计、实施和分析方面的培训。将与部落社区的环境和地政部门建立合作关系，并将为当地社区提供研讨会，以告知他们这项研究的目标、方法和结果。许多植物物种研究发现，物候或形态特征对实验诱导或自然环境变化的可塑性反应，或在不同环境中种群表型选择的强度或方向的变化。然而，到目前为止，还没有研究在物候、形态和生理特征方面跨自然环境梯度实时评估世代之间的进化变化。这项研究将结合对广泛分布的草本植物(Nemophila menziesii，水叶科)种群适合度相关性状地理变异的详细研究，并采取以下措施：对有助于抗旱的性状进行表型选择；适合度加性遗传方差的代际变化；以及对选择的反应，以测试对干旱梯度上环境条件适应性的预测。ASTER模型将用于估计田间条件下家系群体个体适合度的加性遗传方差，并估计物候、形态和生理性状的选择强度和方向。这些模型将有助于对Fisher自然选择基本定理(FFT)的准确性进行实证评估，该基本定理预测种群平均适应度的变化率应等于适应度的加性遗传方差与平均绝对适应度的比率。这一比率代表了一个人口适应当前状况的能力，或其“适应能力”。该项目将是第一个在不同环境梯度的野生种群中进行FFT的严格评估。这项研究将有助于理解自然选择是如何在物种范围内运作的，潜在地识别机制，例如与适应度最优相关的多个特征组合的存在，促进野生种群中遗传变异的维持。

This project will test long-standing evolutionary theory about how rapidly populations can adapt to changing environments by investigating rates of adaptation to intensifying drought in a wild, flowering plant native to California, commonly known as baby blue eyes. The ability of populations to adapt to stressful environmental conditions depends on the presence of genetic variation in survival and reproduction, as well as a genetic variation in the traits that affect survival and reproduction, such as plant physiology and timing of reproduction. Very few studies have measured the process of adaptation to identify the factors that determine how rapidly plant populations adapt to water-limited conditions, in nature. This research will integrate measures of: (1) genetic variation in plant survival and reproduction, both within and among natural populations, as well as in the traits that contribute to plant performance; (2) natural selection in wild populations; and (3) changes between generations in the genetically based aspects of survival and reproduction. Statistical models based on evolutionary theory will be used to predict the magnitude of adaptive change that should occur in each study population. These predictions will be compared to the actual change in survivoral and reproduction observed between generations. Undergraduate students in under-represented groups will be recruited to participate in this research through the Ecological Society of America, the American Indian Science and Engineering Society, and the Society for the Advancement of Chicano and Native Americans in Science. These students will be trained in the design, implementation, and analysis of genetic data collected from field and breeding experiments. Cooperative relationships will be built with the Environmental and Lands departments of Tribal communities, and workshops will be offered to local communities to inform them of the goals, methods, and outcomes of this research.Many studies of plant species have detected plastic responses of phenological or morphological traits to experimentally induced or natural environmental variation, or changes in the strength or direction of phenotypic selection in populations occupying different environments. To date, however, no studies have assessed evolutionary change between generations, in real time, across natural environmental gradients with respect to phenological, morphological, and physiological traits. This study will combine detailed studies of geographic variation in fitness-related traits among populations of a widespread herb (Nemophila menziesii, Hydrophyllaceae) with measures of: phenotypic selection on traits that contribute to drought-tolerance; inter-generational change in additive genetic variance in fitness; and the response to selection in order to test predictions regarding adaptation to environmental conditions across an aridity gradient. Aster models will be used to estimate additive genetic variance in individual fitness in pedigreed populations under field conditions and to estimate the strength and direction of selection on phenological, morphological, and physiological traits. These models will facilitate the empirical evaluation of the accuracy of Fisher's Fundamental Theorem of Natural Selection (FFT), which predicts that the rate of change in population mean fitness should equal the ratio of additive genetic variance in fitness to mean absolute fitness. This ratio represents a population's capacity to adapt to current conditions, or its "adaptive capacity". This project will be the first rigorous evaluation of FFT in wild populations across an environmental gradient. This study will contribute to the understanding of how natural selection operates across a species' range, potentially identifying mechanisms, such as the existence of multiple combinations of traits associated with fitness optima, that promote the maintenance of genetic variation in wild populations.