Effect of multilevel selection on the evolution of gynodioecy

多级选择对雌雄异株进化的影响

• 批准号: RGPIN-2018-04698
• 负责人: Caruso, Christina
• 金额: $ 2.4万
• 依托单位: University of Guelph
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=684678
• 关键词: Effect; multilevel; selection; evolution; gynodioecy

Most traits are thought to evolve because they increase an individual's survival and reproduction. However, there are some traits that appear to decrease an individual's fitness, yet still evolve repeatedly. One such trait is gynodioecy, a type of sexual polymorphism in which hermaphroditic and female plants coexist within a population. Females have an inherent fitness disadvantage because they can reproduce only via seeds, whereas hermaphrodites can reproduce via both seeds and pollen. Despite this disadvantage, females, and thus gynodioecy, have evolved repeatedly in the flowering plants. Females could evolve in response to individual-level selection that acts only under a restricted set of conditions, or in response to selection at levels above and/or below the individual, including the group and the gamete. Measuring selection at multiple levels is important because traits evolve differently based on the level at which selection acts: even when the strength and direction of selection are similar across levels, both the causes of and responses to selection can differ.******Our long-term goal is to determine how the evolution of gynodioecy has been affected by selection at multiple levels. Our recent work suggests that gynodioecy can evolve in response to frequency-dependent selection (where an individual's fitness depends in part on the mean phenotype of its group) and gametic selection (where the viability of a gamete depends on which allele it carries). However, we also found that the frequency of females varies widely among gynodioecious populations, suggesting that the strength of selection varies. ******To determine the why the strength of selection varies among gynodioecious populations, we will focus on two short-term goals. First, we will identify the mechanisms that cause frequency-dependent selection on female plants by testing why females have frequency-dependent fitness and whether the strength of frequency-dependent selection depends on conspecific density. Second, we will identify the mechanisms that cause gametic selection on sex-determining genes by testing whether variation in the strength of gametic selection is caused by ecological or genetic factors and whether these genetic factors are in the cytoplasmic or nuclear genome. All of this work will be done in the gynodioecious species Lobelia siphilitica. ******Although gynodioecy was first studied by Darwin, there is still uncertainty as to why it evolves in some populations but not in others. The proposed research, by focusing on the mechanisms that cause frequency-dependent selection and gametic selection, will allow us to predict the ecological and genetic contexts in which gynodioecy is more and less likely to evolve. More generally, the proposed research will demonstrate how measuring selection at multiple levels can lead to new explanations for the repeated evolution of traits that appear to decrease an individual's fitness. *****

大多数特征被认为是进化的，因为它们增加了个体的生存和繁殖。然而，有一些特征似乎会降低个体的适应性，但仍然会反复进化。其中一个特征是雌雄异株，这是一种两性植物和雌性植物在种群中共存的性别多态性。雌性有一个固有的适应性劣势，因为它们只能通过种子繁殖，而雌雄同体可以通过种子和花粉繁殖。尽管有这个缺点，雌性，因此雌蕊异株，在开花植物中反复进化。雌性动物的进化可能是为了响应个体水平的选择，这种选择只在有限的条件下起作用，或者是为了响应高于和/或低于个体水平的选择，包括群体和配子。在多个层面上衡量选择是很重要的，因为性状的演变取决于选择作用的水平：即使选择的强度和方向在各个层面上相似，选择的原因和反应也可能不同。我们的长期目标是确定如何在多个层面上选择的影响，雌核双极体的进化。我们最近的工作表明，雌核双极体可以在频率依赖性选择（个体的适应性部分取决于其群体的平均表型）和配子选择（配子的生存能力取决于它携带的等位基因）的反应中进化。然而，我们也发现雌性的频率在雌雄异株的种群中变化很大，这表明选择的强度不同。* 为了确定为什么选择的强度在雌雄异株种群中不同，我们将关注两个短期目标。首先，我们将确定的机制，导致频率依赖性选择雌性植物测试为什么女性有频率依赖性健身和频率依赖性选择的强度是否取决于同种密度。第二，我们将通过测试配子选择强度的变化是否是由生态或遗传因素引起的，以及这些遗传因素是否在细胞质或核基因组中，来确定导致配子选择性别决定基因的机制。所有这些工作都将在雌花异株的物种半边莲中进行。** 虽然雌蕊异花首先由达尔文研究，但仍然不确定为什么它在某些种群中进化而不是在其他种群中进化。这项拟议的研究，通过关注导致频率依赖性选择和配子选择的机制，将使我们能够预测雌核发育的生态和遗传背景。更一般地说，拟议中的研究将展示如何在多个层面上测量选择，从而为似乎会降低个体适应性的特征的重复进化提供新的解释。*****