Evolution of Dioecy from Distyly and the Impact of Recent Landscape Changes on the Reproductive Systems of Cordia spp in the Guanacaste Region of Costa Rica

[02:12 . 42]生殖系统是植物生命史的一个重要特征，其多样性和可变性是众所周知的。两种特别值得注意的繁殖系统是单株和雌雄异株。具有两种类型的自交不亲和雌雄同体个体的diyly在开花植物中已经进化了多次。两种类型的个体（长花柱和短雄蕊的个体（别针）和短花柱和长雄蕊的个体（线头））的交配通常仅限于类型之间的杂交。雌雄异株种，另一方面，有单独的雄性和雌性（单性）个体。有许多近亲物种（Cordia spp.）拥有这些可选择的繁殖策略的例子，并且一再提出雌雄异株是从雌雄异株进化而来的。然而，目前还没有基因测试或生态学研究来证实或反驳这种进化途径的可能性。本研究的第一个目的是利用分子系统发育技术重建科迪亚的系统发育，并将育种系统的变化映射到它上面。第二个目标是使用DNA标记来识别雌雄异株物种中与性别决定基因相关的区域，以及在二花物种中与花形态（针状花序和线状花序）相关的区域。这些标记将被用来描述每个育种系统的遗传基础，共同起源的可能性，以及导致变化的具体步骤。这些研究将提供有关热带树木繁殖系统进化变化方向的信息。这项工作将为未来研究在快速变化的环境下（例如，由景观级干扰引起的传粉者群落的变化）繁殖系统进化如何发生奠定基础，这是保护生物学中相当重要的课题。该研究还将影响人力资源开发，因为pi坚定地致力于为女学生和来自科学领域代表性不足的群体的学生提供研究机会（例如，通过我们的本科生暑期研究经验（REU）项目、麦克奈尔奖学金和环境生物学本科生指导（UMEB））。此外，该项目还将培养研究生和博士后助理。

0212742BawaBreeding systems, a keystone feature of the life history of plants, are known to be diverse and mutable. Two breeding systems of particular note are distyly and dioecy. Distyly, with self-incompatible hermaphroditic individuals of two types, has evolved multiple times in flowering plants. Mating of the two types of individuals, (those with long styles and short stamens (pin) and those with short styles and long stamens (thrum)), is generally restricted to crosses between types. Dioecious species, on the other hand, have separate male and female (unisexual) individuals. There are many examples of closely related species (Cordia spp. is one) that possess these alternative breeding strategies and it has been repeatedly suggested that dioecy has evolved from distyly. Yet no genetic tests nor ecological studies have been made to confirm or refute the likelihood of this evolutionary pathway. The first objective of this research is to use molecular phylogenetic techniques to reconstruct the phylogeny of Cordia spp. and to map changes in breeding system onto it. The second objective is to use DNA markers to identify regions linked to sex-determining genes in dioecious species and to flower morphology (pin and thrum) in distylous species. These markers will be utilized to characterize the genetic basis of each breeding system, the likelihood of a common origin, and the specific steps that lead to changes. These studies will provide information about the direction of evolutionary change in breeding systems in a tropical tree. This work will lay the foundation for future studies on how breeding system evolution occurs within the context of rapidly changing environments (e.g., changes in the pollinator community brought on by landscape-level disturbance), a topic of considerable importance for conservation biology. The research will also impact human resource development because of PIs' strong commitment to provide research opportunities for female students and for students from groups under-represented in science (e.g., through our summer Research Experience for Undergraduates (REU) programs, McNair fellowships and Undergraduate Mentoring in Environmental Biology (UMEB)). In addition the project will train graduate students and post doctoral associates.