Mutation, Selection and Divergence of Plant Populations

进化生物学试图了解地球上生命多样性背后的过程。目前所有的多样性--无论是物种、种群或个体之间的多样性--都源于突变。在地理上分离的种群中积累的突变会产生表型分歧和生殖隔离，这是形成新物种的第一步。这里提出的研究将解决突变如何导致种群分化和红衣藻繁殖隔离的问题，红衣藻是一种分布广泛的二倍体物种，从加拿大南部到中美洲。由于植物的多重亲子关系，植物的雄性和雌性功能具有不同的最适后代供应水平。女性父母与她们的后代各有一半的血缘关系。相比之下，男性父母只与自己的后代有一半的亲缘关系，与其他父系的后代的亲缘关系不到一半。这种差异产生了性别冲突：理论上，女性父母从平等提供所有子女中受益，而每一位男性父母受益于以牺牲其他男性为代价，更多地提供自己的子女。我们(1)发现地理上不同的红衣主教种群之间的杂交通常会产生异常小或大的种子，并开发了(2)测试性别冲突的证据和(3)将性冲突与其他导致提供异常后代的原因区分开来的方法。这组项目将研究因性别冲突在地理上分离的人口中独立演变而产生的生殖隔离的基因组学和发育生物学。我们最近发现，地理上分离的红衣藻种群之间的实验杂交总是会产生种子，但根据种群对和杂交方向的不同，种子要么都是有性的，要么都是无性的(无融合生殖)。被子植物的有性种子生产涉及胚胎和胚乳中母本和父本基因组之间一系列复杂的协调相互作用。授粉后的无融合生殖代表完全的交配后生殖隔离。利用我们实验室开发的分子和显微技术，我们将探索红花无融合生殖的基因组、遗传和发育基础，包括重复元件的作用和基因组大小。因此，这套项目将解决无融合生殖和交配后生殖隔离的进化起源，这是物种形成的一个决定性步骤。这项拟议的研究旨在增进我们对突变和选择在塑造植物进化和种群分化中的组合作用的理解。这些项目在生物信息学、计算机模拟、共焦显微镜、统计分析和田间生物学等几个领域为研究生和本科生提供了现代和高级培训机会。

Evolutionary biology seeks to understand the processes underlying the diversity of life on earth. All current diversity-whether among species, populations or individuals-originated by mutation. Mutations accumulating in geographically separated populations can generate both phenotypic divergence and reproductive isolation, the first step in the formation of new species. The research proposed here will address how mutations cause population divergence and reproductive isolation within Lobelia cardinalis, a widespread diploid species ranging from southern Canada to Central America. Because of multiple paternity, the male and female functions of plants have different optimal levels of offspring provisioning. Female parents are related by half to each of their offspring. Male parents, in contrast, are related by half only to their own offspring and by less than half to offspring of other sires. This difference generates a sexual conflict: in theory, female parents benefit from equal provisioning of all offspring, while each male parent benefits by higher provisioning of its own offspring at the expense of other males. We have (1) discovered that crosses between geographically divergent L. cardinalis populations often result in abnormally small or large seeds and developed methods (2) to test for evidence of sexual conflict and (3) to distinguish sexual conflict from other causes of abnormal offspring provisioning. This set of projects will investigate both the genomics and developmental biology of reproductive isolation arising from sexual conflict evolving independently in geographically separated populations. We have recently discovered that experimental crosses among geographically separate populations of L. cardinalis always produce seeds but that, depending on the population pair and the crossing direction, the seeds are either all sexual, all asexual (apomictic) or a mixture. Sexual seed production in angiosperms involves a complex set of coordinated interactions between maternal and paternal genomes in both embryo and endosperm. Apomixis following pollination represents complete post-mating reproductive isolation. Using molecular and microscopy techniques developed in our lab, we will explore the genomic, genetic and developmental basis of apomixis in L. cardinalis, including the role of repetitive elements and genome size. This set of projects will thus address the evolutionary origin of both apomixis and post-mating reproductive isolation, a defining step in speciation. The proposed research aims to advance our understanding of the combined roles of mutation and selection in shaping plant evolution and the divergence of populations. The projects provide modern and advanced training opportunities at both the graduate and undergraduate levels in several areas including bioinformatics, computer-based simulation, confocal microscopy, statistical analysis and field biology.