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，这与理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，许多基因位于同一DNA片段上的事实，使得自然选择很难对每一个基因有效地发挥作用，这一现象被称为克隆干扰。这限制了进化的最大速度，在不断变化的环境中，进化太慢的种群会灭绝。这项研究将通过数学模型来解决这些问题，这些模型将计算克隆干扰对物种灭绝的影响，并分析竞争的性质。该研究项目还将通过公开讲座、科普书籍和维基百科文章为本科生提供培训，包括来自科学代表性较低群体的个人，并通过公共讲座、科普书籍和维基百科文章向普通公众提供教育。最近的证据表明，高水平的连锁不平衡意味着重组在相同的基因背景下将适应性突变聚集在一起的速度很慢。不同的适应性基因类型相互竞争，导致许多适应性丧失而不是修复。为了解决在不断变化的环境中由于克隆干扰导致灭绝而导致的缓慢适应这一主题，研究人员将开发进化救援(自适应逃脱灭绝)的数学模型。研究人员提出了一种新的三维适应度方案：R-选择低人口密度下的绝对增长速度，K-选择资源利用的绝对效率，C-选择高人口密度下的相对竞争力。与过去的2D方案相比，该3D方案具有显著的优势，例如，r与K、相对与绝对、硬与软、组与个人。这种新的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应度维度，既有可能进行权衡，也有可能产生协同效应。常见的组合表示突变和适应的自然轴。初步数据表明，这是一个与密度无关的适合度的自然轴，沿着这一轴，环境变化会同等比例地降低r和K，而随后的适应(进化拯救)则会增加这两个值。在克隆干扰存在的情况下的适应将仅在这个维度中建模，也在第二维度的存在中建模。后者将展示助长c-选择相对军备竞赛的突变如何通过克隆干扰沿绝对适应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.