Ecological effects of clonal interference in a changing environment

这项研究将促进我们对进化如何进行以及进化变化的最大速度可能是多少的理解，这与了解种群是否能够足够快地适应以避免在当今快速和全球变化的环境中灭绝有关。最近的证据表明，许多基因驻留在相同的DNA片段上，这使得自然选择很难对每个基因有效地起作用，这种现象被称为克隆干扰。这限制了进化的最高速度，在不断变化的环境中，进化太慢的种群会灭绝。本研究将通过数学模型来解决这些问题，该模型将计算克隆干扰对灭绝的影响，并分析竞争的本质。该研究项目还将为本科生提供培训，包括来自科学领域代表性不足群体的个人，并通过公开讲座、科普书籍和维基百科文章为公众提供教育。最近的证据表明，高水平的连锁不平衡意味着，在相同的遗传背景下，重组将适应性突变聚集在一起的速度很慢。不同的适应性基因型相互竞争，导致许多适应性丧失而不是固定下来。为了解决在不断变化的环境中由于克隆干扰导致灭绝的缓慢适应这一主题，研究人员将开发进化拯救（适应性逃离灭绝）的数学模型。提出了一种新的三维适应度方案：低种群密度下的绝对生长速度选择r，资源利用绝对效率选择k，高种群密度下的相对竞争能力选择c。与过去的2D方案相比，这种3D方案具有显著的优势，例如，r vs K，相对vs绝对，硬vs软，群体vs个人。这种新颖的3D（和可扩展的）模型将被开发并应用于现有的模型系统和数据。每个适应性突变都会影响一个或多个适合度维度，可能存在权衡和协同作用。常见的组合表明突变和适应的自然轴。初步数据表明存在一条与密度无关的自然适应度轴，沿着这条轴，环境变化会等比例地降低r和K，而随后的适应（进化拯救）则会提高r和K。克隆干扰存在时的适应将仅在这个维度上建模，也将在第二个维度上建模。后者将展示突变如何推动c选择的相对军备竞赛，可能通过克隆干扰沿着绝对适合度轴的进化拯救而导致灭绝。

This research will advance our understanding of how evolution proceeds and what the maximum rate of evolutionary change might be, which is relevant to understanding whether populations will be able to adapt fast enough to avoid extinction in today's rapidly and globally changing environment. Recent evidence suggests that the fact that many genes reside on the same stretches of DNA makes it difficult for natural selection to act effectively on each one, in a phenomenon known as clonal interference. This limits the maximum speed of evolution, and in a changing environment, populations that evolve too slowly go extinct. This study will address these questions through mathematical models that will calculate the impact of clonal interference on extinction and analyze the nature of competition. This research project also will provide training for undergraduate students, including individuals from groups underrepresented in the sciences, and education for the general public through public lectures, a popular science book, and Wikipedia articles.Recent evidence suggests that high levels of linkage disequilibrium imply that recombination is slow to bring adaptive mutations together on the same genetic background. Different adaptive genotypes compete, causing many adaptations to be lost instead of fixed. To address this topic of slow adaptation due to clonal interference leading to extinction in a changing environment, the researcher will develop mathematical models of evolutionary rescue (adaptive escape from extinction). The researcher proposes a new three dimensional fitness scheme: r-selection for absolute growth speed at low population density, K-selection for absolute efficiency of resource use, and c-selection for relative competitive ability at high population density. This 3D scheme has significant advantages over past 2D schemes, e.g., r vs. K, relative vs. absolute, hard vs. soft, groups vs. individuals. This novel 3D (and extensible) model will be developed and applied to existing model systems and data. Each adaptive mutation affects one or more fitness dimensions, with both tradeoffs and synergies possible. Common combinations indicate natural axes of mutation and adaptation. Preliminary data suggest a natural axis of density-independent fitness, along which environmental change lowers both r and K in equal proportions, while subsequent adaptation (evolutionary rescue) increases both. Adaptation in the presence of clonal interference will be modeled in this dimension alone, and also in the presence of a second dimension. The latter will show how mutations fuelling the relative arms race of c-selection might contribute to extinction via clonal interference with evolutionary rescue along an absolute fitness axis.