DISSERTATION RESEARCH: How is the Selfing Syndrome Assembled? A Common Garden Fitness Study of its Component Parts

这个项目将测试植物为什么会自花授粉的五种进化解释，这将加深我们对植物进化的一个重要特征的理解，并将改进我们的自花授粉作物的育种，如西红柿、玉米和大豆。植物的繁殖方式多种多样，10%-15%的植物主要是自花授粉。从异交到自交的进化转变往往伴随着许多花卉性状的减少。研究人员将在牵牛花中确定这些变化的遗传基础。这些研究物种与甘薯密切相关，甘薯是一种关键的全球食物资源，已被证明对现代选择性育种具有挑战性。在这项研究中开发的遗传资源可能有助于创造更有活力和抗病的甘薯。向自交的过渡通常伴随着花大小、花蜜产量、花粉-胚珠比率、色素沉着和花药与柱头之间的距离的减少，统称为自交综合征。5种自交综合征进化模型(资源分配、边缘环境和植物区系、自交效率和对近交衰退的普遍缩小)将通过田间试验和温室试验相结合的方式进行检验。研究人员将开发牵牛花物种Ipomoea lacunosa和它的姐妹物种I.cordatotrioba之间的杂交回交系。Ipomoea lacunosa是一种自交物种，它的姐妹种I.cordatotrioba既能进行杂交，又能进行自花授粉。该项目将确定(1)自交综合征特有的空心菜性状是由于直接选择而进化的，还是与其他性状的选择相关的反应，以及(2)什么选择压力鼓励采用自交综合征。研究人员将在一项由2400个来自一组近等基因系和野生型对照的个体组成的田间实验中，测量对自交综合征的三个性状(花粉数量、花蜜体积和花冠大小)的选择。适合性将通过三个替代指标进行评估：移植后的存活率、结实率和异交亲缘关系。

This project will test five evolutionary explanations for why plants self-pollinate, which will deepen our understanding of an important characteristic of plant evolution and will improve our breeding of self-pollinating crops such as tomatoes, corn and soybeans. Plants reproduce in a variety of ways, and 10-15% of plant species are primarily self-pollinating. The evolutionary transition from outcrossing to selfing is often accompanied by reductions in many floral traits. The researchers will determine the genetic bases for these changes in the morning glory. The study species are closely related to the sweet potato, a key global food resource that has proven challenging for modern selective breeding. Genetic resources developed in this study may help in the creation of more vigorous and disease-resistant sweet potatoes.The transition to selfing is often accompanied by reductions in flower size, nectar production, pollen-ovule ratio, pigmentation, and the distance between the anther and stigma, collectively called the selfing syndrome. Five models of selfing syndrome evolution (resource allocation, marginal environment and florivory, efficiency of autogamous selfing, and general size reduction in response to inbreeding depression) will be tested by a combination of field and greenhouse experiments. Researchers will develop hybrid backcrossed lines between the morning glory species Ipomoea lacunosa, a selfing species, and its sister species, I. cordatotriloba, which both outcrosses and self-pollinates. The project will determine (1) whether traits in I. lacunosa characteristic of the selfing syndrome evolved in response to direct selection or were correlated responses to selection on other traits and, (2) what selective pressures encourage the adoption of the selfing syndrome. The investigators will measure selection on three selfing syndrome traits (pollen number, nectar volume, and corolla size) in a field experiment comprising 2400 individuals from a set of nearly isogenic lines and wild-type controls. Fitness will be assessed through three proxy measures: survival after transplant, seed set, and outcross paternity.