Collaborative Research: The Evolution of Life History, Physiological, and Floral Traits in Clarkia: do Genetic Correlations affect Mating System Evolution?

大多数开花植物依靠动物为它们的花授粉，在大多数情况下，这种授粉会导致交叉受精(即不同个体之间的交配)。然而，近25%的物种经常进行自花授粉，花粉在同一植物的花内或花间转移。在自然种群中，自我受精导致个体及其后代的遗传变异减少，这与栽培作物近亲繁殖的影响类似。鉴于这种遗传变异的丧失存在许多潜在的生态和进化劣势，许多植物物种的自花受精进化仍然是个谜。到目前为止，对这一现象的大多数解释都提出了生殖优势可能会超过已知的遗传劣势。例如，当传粉者稀少或不可靠时，或者当较短的生长季节有利于快速繁殖时，自然选择可能有利于自花授粉。然而，自交通常伴随着一系列生理、形态和生活史性状一起进化，这提出了另一种可能性，即它的进化受到与其在发育、生理或遗传上相关的其他性状的选择的影响。这项研究的目的是为这一替代解释寻找证据。具体地说，研究人员将结合数量遗传学和生理学方法，检验这样一种假设，即自交可以作为(A)影响自交受精率的花性状和(B)使植物逃脱干旱的生活史或生理性状之间遗传相关性的结果而进化。如果生活史或生理特征的选择确实影响自交率，这将对种群的遗传结构产生连锁效应，潜在地限制它们适应未来环境变化的能力。一年一度的野生花属Clarkia(Onagraceae)为研究这种影响提供了一个丰富的机会，因为它包括几个自花受精独立进化的物种。更广泛的影响：该项目将启动四个个人投资机构之间的协作和互惠培训，并包括至少15名本科生参加，其中包括任职人数不足的群体。PIS将与加州大学圣巴巴拉分校的“大自然中的孩子”项目合作，将研究和教育结合起来。此外，物种和亚种之间的生理比较可能产生关于物种分布变化的预测，以及在内华达山脉南部预计将在未来几年经历越来越频繁的干旱的情况下与近亲繁殖相关的遗传风险。

The majority of flowering plant species rely on animals to pollinate their flowers, and in most cases such pollination results in cross-fertilization (i.e., mating between different individuals). However, nearly 25% of species regularly self-fertilize, with pollen being transferred within or between flowers on the same plant. Within natural populations, self-fertilization causes a reduction in genetic variation within individuals and their descendents, in a similar way to the effects of inbreeding in cultivated crops. Given that there are many potential ecological and evolutionary disadvantages to this loss of genetic variation, the evolution of self-fertilization in many plant species remains enigmatic. To date, most explanations for the phenomenon have proposed reproductive advantages that could outweigh the known genetic disadvantages. For example, natural selection might favor self-fertilization when pollinators are scarce or unreliable, or when short growing seasons favor rapid reproduction. However, selfing often evolves along with a suite of physiological, morphological, and life history traits, which raises the alternative possibility that its evolution is influenced by selection on other traits with which it is developmentally, physiologically, or genetically correlated. The goal of this research is to seek evidence for that alternative explanation. Specifically, using a combination of quantitative genetic and physiological approaches, the investigators will test the hypothesis that selfing can evolve as a consequence of genetic correlations between (a) floral traits that affect the rate of self-fertilization and (b) life history or physiological traits that enable plants to escape drought. If selection on life history or physiological traits does influence selfing rates, this will have cascading effects on the genetic structure of populations, potentially limiting their ability to adapt to future environmental change. The annual wildflower genus Clarkia (Onagraceae) provides a rich opportunity to investigate such effects because it includes several species in which self-fertilization has evolved independently. Broader impacts: This project will initiate a collaboration and reciprocal training among four PIs and include the participation of at least 15 undergraduates, including those of under-represented groups. PIs will work with the University of California, Santa Barbara's "Kids in Nature" program to integrate research and education. In addition, physiological comparisons between species and subspecies may generate predictions about changes in species' distributions and the genetic risks associated with inbreeding in the face of an increasing frequency of droughts that the southern Sierra Nevada is expected to experience in coming years.