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生于加州的野生开花植物（俗称“蓝眼睛”）对日益严重的干旱的适应速度，来检验长期存在的进化理论，即种群适应不断变化的环境的速度有多快。种群适应压力环境条件的能力取决于生存和繁殖中存在的遗传变异，以及影响生存和繁殖的性状中的遗传变异，如植物生理和繁殖时间。很少有研究测量了适应过程，以确定决定植物种群适应自然界缺水条件的速度的因素。本研究将整合以下措施：(1)植物生存和繁殖的遗传变异，包括自然种群内和种群间的遗传变异，以及对植物性能有贡献的性状；(2)野生种群的自然选择；(3)世代之间基于生存和繁殖的遗传方面的变化。基于进化理论的统计模型将用于预测每个研究群体中应该发生的适应性变化的幅度。这些预测将与在世代之间观察到的生存和繁殖的实际变化进行比较。本研究将通过美国生态学会、美国印第安人科学与工程学会、墨西哥裔美国人和印第安人科学促进会等组织招募代表性不足群体的本科生参与。这些学生将接受设计、实施和分析从田间和育种实验中收集的遗传数据的培训。将与部落社区的环境和土地部门建立合作关系，并将向当地社区提供讲习班，告知他们这项研究的目标、方法和结果。许多植物物种的研究已经发现物候或形态性状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强度或方向的变化。然而，到目前为止，还没有研究在自然环境梯度中实时评估代际间的物候、形态和生理特征的进化变化。本研究将结合一种广泛分布的草本植物（Nemophila menziesii, hydrophyllacae）种群中适应性相关性状的地理变异的详细研究，并测量：有助于耐旱性状的表型选择；适应性加性遗传变异的代际变化以及对选择的反应，以测试关于在干旱梯度上适应环境条件的预测。Aster模型将用于估计野外条件下纯种群体个体适应度的加性遗传变异，并估计物候、形态和生理性状的选择强度和方向。这些模型将有助于实证评估费雪自然选择基本定理（FFT）的准确性，该定理预测种群平均适应度的变化率应该等于适应度中加性遗传方差与平均绝对适应度的比值。这个比率代表了人口适应当前条件的能力，或其“适应能力”。该项目将是跨环境梯度野生种群FFT的首次严格评估。这项研究将有助于理解自然选择如何在物种范围内运作，潜在地确定机制，例如与适应度最优相关的多种性状组合的存在，促进野生种群遗传变异的维持。

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.