Coevolutionary Arms Races Driven by Conflict: a Test in Social Amoeba

冲突驱动的共同进化军备竞赛：对社会阿米巴原虫的考验

• 批准号: 1557023
• 负责人: Rebecca Zufall
• 金额: $ 69.66万
• 依托单位: University of Houston
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-04-01 至 2020-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1557023&HistoricalAwards=false
• 关键词: Coevolutionary; Arms; Races; Driven; Conflict

Cooperation is observed across all levels of biological organization: genomes cooperate within cells, cells cooperate within multicellular organisms, and individuals cooperate to form societies. However, at each of these levels, there are some individuals who cheat and others who do not, and biologists still do not fully understand how populations evolve stable systems with both types of individuals or how this coevolution is distributed across populations of the same species in nature. This is because individuals who cheat gain the benefits of cooperation without paying their fair share of the cost, and thus this should spread rapidly through populations. Studying the natural distributions of cheating and cooperation in populations is important because cheating is prevalent in the natural world and occurs across all levels of biological organization, from genes that enhance their own transmission to the detriment of the individual that harbors them, to brood parasites that trick others into raising their young. More importantly, the evolution of mechanisms to prevent cheating was likely critical to the emergence of biological complexity. Moreover, cheating can influence everything from the success of symbioses to the emergence of cancer, and thus has important applications to both medicine and agriculture. The novelty of this project is that the researchers will document natural populations of a slime mold in the wild to determine if there is variation (and coevolution) in the degree of cheating and in resistance to cheating across space and through time. The research also takes a population genomic approach to determine the genes involved in cheating and resistance. Overall the goal is to understand the ecological and evolutionary processes influencing the dynamics of cheating in nature. One prominent hypothesis is that cheating selects for mechanisms to resist or suppress it, which in turn selects for mechanisms to overcome that resistance. Cheating might thus give rise to an arms race of adaptations and counter-adaptations. If so, then social conflict, just like other forms of selective conflict, may cause rapid, divergent, and never-ending change, driving evolutionary divergence and diversification. To date, this arms race hypothesis has garnered support from laboratory experiments and molecular evolution analyses, but there is no work examining how cheating impacts the evolutionary trajectories of social traits in nature. The goal of this research is to test several predictions of this hypothesis in natural populations of the social amoeba (or cellular slime mold) Dictyostelium discoideum. This organism has an unusual form of multicellularity that renders it particularly vulnerable to cheating. The research will quantify phenotypic patterns of adaptation and counter-adaptation in nature, inspired by approaches used to elucidate other forms of selective conflict, such as host-pathogen or genetic conflict. Longitudinal sampling across space and time, combined with the ability to save and revive past and future social partners, offers a unique opportunity to observe coevolution in situ and constitutes a major advantage over other model systems.

在生物组织的所有层面上都可以观察到合作：基因组在细胞内合作，细胞在多细胞有机体内合作，个人合作形成社会。然而，在这些水平上，都有一些作弊的个体和另一些不作弊的个体，生物学家仍然不能完全理解种群如何进化出具有这两种类型的个体的稳定系统，或者这种共同进化是如何在自然界中同一物种的种群中分布的。这是因为作弊的个人在没有支付公平份额的成本的情况下获得了合作的好处，因此这种情况应该在人群中迅速传播。研究欺骗和合作在种群中的自然分布是很重要的，因为欺骗在自然界中很普遍，发生在生物组织的各个层面，从增强自身传播的基因到损害携带它们的个人的基因，到诱骗他人抚养后代的幼虫。更重要的是，防止作弊机制的进化可能对生物复杂性的出现至关重要。此外，作弊可以影响从共生成功到癌症出现的方方面面，因此在医学和农业方面都有重要的应用。这个项目的新奇之处在于，研究人员将记录野生粘菌的自然种群，以确定在作弊程度和对作弊的抵抗力方面是否存在变异(和共同进化)，跨越空间和时间。这项研究还采用了群体基因组方法来确定与欺骗和抵抗力有关的基因。总体而言，我们的目标是了解影响自然界作弊动态的生态和进化过程。一个突出的假设是，作弊选择了抵抗或抑制作弊的机制，而作弊又选择了克服这种抵触的机制。因此，作弊可能会引发一场适应和反适应的军备竞赛。如果是这样，那么社会冲突，就像其他形式的选择性冲突一样，可能会导致快速、分歧和永无止境的变化，推动进化分歧和多样化。到目前为止，这一军备竞赛假说得到了实验室实验和分子进化分析的支持，但还没有研究作弊如何影响自然界中社会特征的进化轨迹。这项研究的目的是在社会阿米巴(或细胞黏菌)盘基网柄菌的自然种群中检验这一假说的几个预测。这种有机体具有一种不同寻常的多细胞结构，这使得它特别容易受到欺骗。这项研究将量化自然界中适应和反适应的表型模式，灵感来自于用于阐明其他形式的选择性冲突的方法，如宿主-病原体或遗传冲突。跨越空间和时间的纵向采样，再加上拯救和复兴过去和未来的社会伙伴的能力，为现场观察共同进化提供了独特的机会，构成了相对于其他模型系统的主要优势。