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

0212742 Bawa育种系统，植物生活史的一个关键特征，已知是多样的和可变的。两个特别值得注意的育种系统是distilyly和diophilic。 二花柱，具有两种类型的自交不亲和的两性个体，在显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（针）和短花柱和长雄蕊的个体（线））的交配通常限于类型之间的杂交。 另一方面，雌雄异株的物种有单独的雄性和雌性（单性）个体。 有许多例子密切相关的物种（Cordia spp.）。是一个），拥有这些替代育种策略，并已多次提出，diophyll已演变从distysly。 然而，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学技术重建Cordia spp.的系统发育。第二个目标是利用DNA标记来鉴定雌雄异株物种中与性别决定基因相关的区域和二端物种中与花形态（针和线头）相关的区域。 这些标记将用于表征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育种系统进化变化方向的信息。这项工作将为未来研究育种系统如何在快速变化的环境中进化奠定基础（例如，在传粉昆虫群落的变化所带来的干扰水平），一个相当重要的保护生物学的主题。 这项研究还将影响人力资源开发，因为PI坚定地承诺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）计划，麦克奈尔奖学金和环境生物学本科生导师（UMEB））。 此外，该项目还将培训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.