Collaborative Research: Does genetic load drive mating system evolution? Tests in an explicit historical context

这项研究将量化形成植物交配系统的历史事件和当前自然选择之间的相互作用。进化是一个持续的过程，但强烈依赖于过去。虽然几乎每个人都承认这一事实，但很难量化历史和当前的选择压力作为对自然界模式的解释的相对重要性。这项研究将着眼于决定美国风铃花(风铃花)自花授粉与异交数量的因素。该项目将使本科生和研究生沉浸在收集下一代DNA序列数据中，以重建历史事件和对研究物种当前选择环境的研究。将来自这些不同来源的数据分析到一个单一的、统一的框架中，将提供对自然界中形成复杂模式的过程的更清晰的理解，并产生一个可应用于任何生物系统的预测性框架。这种预测方法的广泛传播是有价值的，因为它将有助于预测物种对现代日益变化的环境的反应。植物交配系统在进化上是不稳定的，从高度异交到高度近亲繁殖。这种广泛的差异为理解进化变化的最终驱动力提供了一个极好的系统。生物层级之间的可变交配系统策略通常被解释为对当前选择性环境的适应。然而，这种变异的很大一部分可能反映了在活动范围扩大期间响应殖民的历史进化。这一想法将用一种北美草本植物--美洲风铃草进行测试，初步数据表明，在系统地理数据表明最近殖民的地点，近亲交配衰退减少，自交性增加。使用距离冰川避难所一定范围的种群，研究人员将通过对RAD-Seq多态的联合分析、固定和分离遗传负荷的温室研究、花粉限制和生殖保证的实地研究以及自交率的种群遗传推断来收集数据。对这些数据的分析将确定最初与射程扩大相关的非适应性过程是否为交配系统的后来进化提供了一个允许的环境。因此，研究框架提供了一种机制，用于识别过去和现在时间尺度上生物体变化的最终驱动因素。

This research will quantify the interplay between historical events and current natural selection in shaping plant mating system. Evolution is an ongoing process but depends strongly on the past. While nearly everyone acknowledges this fact, it has been difficult to quantify the relative importance of historical and current selection pressures as explanations of patterns in nature. This research will look at the factors that have determined the amount of self-pollination versus outcrossing in the American bellflower (Campanulastrum americanum). The project will immerse undergraduate and graduate students in the collection of next-generation DNA sequence data to reconstruct historical events and studies of current selective environment in the study species. Analyses of data from these disparate sources into a single, unified framework will provide a clearer understanding of the processes shaping complex patterns in nature, and yields a predictive framework that can be applied in any biological system. Broad dissemination of this predictive approach is valuable because it will help predict the response of species to increasingly altered environments in the modern age.Plant mating systems are evolutionarily labile, ranging from highly outcrossing to highly inbreeding. This wide variation provides an excellent system for understanding the ultimate drivers of evolutionary change. Variable mating system strategies across levels of the biological hierarchy are commonly explained as adaptations to the current selective environment. A significant fraction of this variation, however, may reflect historical evolution in response to colonization during range expansion. This idea will be tested using Campanulastrum americanum, a North American herb in which preliminary data indicate reduced inbreeding depression and greater autogamy in sites where phylogeographic data suggest recent colonization. Using populations a range of distances from glacial refugia, the researchers will gather data with coalescent analysis of RAD-seq polymorphism, greenhouse studies of fixed and segregating genetic load, field studies of pollen limitation and reproductive assurance, and population-genetic inferences of selfing rates. Analyses of these data will determine whether initially non-adaptive processes associated with range expansion provided a permissive environment for later evolution of the mating system. The research framework therefore provides a mechanism for discerning the ultimate drivers of organismal change across past and present time scales.