Dissertation Research: Addressing "The Hardest Puzzle in American Pomology" - the Systematics of Prunus Section Prunocerasus (Rosaceae)

李属(蔷薇科)是北半球温带植物的一个大属，约有200种，包括李子/李子、桃、杏、樱桃和杏子等重要的经济树种。北美李群包括大约13-17个物种，它们之间的亲缘关系如此密切，以至于它们没有建立生殖障碍，并且经常杂交。由于它们很容易杂交，物种的界限很难划定，因此北美李种的区分和分类长期以来一直很困难。北美李子是系统研究(研究有机体的种类和多样性以及它们之间关系的研究)的有趣模式，因为它们处于系统发育(研究物种之间的进化关系)和种群遗传学(研究物种种群之间的遗传变异模式)的交界处。因此，这项研究不仅将有助于解决密切相关物种群体之间的关系，而且还将测试密切相关物种群体的系统发育解析的限度。进化上密切相关的物种群体，在形态上很难区分，可以用遗传数据进行分析。本研究的目的是利用DNA序列数据分析北美李属植物之间的进化关系。通过比较每个推定种的多个种质的DNA序列，我们可以推断每个种内存在多少遗传变异，以及推定种之间存在多少遗传分化。这项研究将对学术界非常重要，因为它将作为对非常密切的物种群体的基线调查。李属中的许多物种作为观赏植物或粮食作物(如李子/李子、桃子、杏子、樱桃和杏子)具有重要的经济价值。欧亚李是最常用于农业的李，但由于不能很好地适应环境条件或疾病，在北美许多地区很难种植。这项研究的重点北美本土李子并没有大规模种植，尽管一些物种目前正在作为潜在的粮食作物进行调查。大多数李子作物物种是由少数欧亚本土李子杂交而来的。由于北美原生李品种较多，通过杂交改良品种的潜力更大。除了它们潜在的经济重要性外，几种北美李子在国家一级也受到保护。此外，灌木李(P.genrulata)是联邦濒危物种，仅限于佛罗里达州中部的四个县，那里的栖息地因开发而丧失，严重危及其栖息地。因此，了解北美原产李的分类和进化历史具有重要的经济意义以及保护和生物学意义。最后，这项工作将对农业和园艺界有用，因为李子在园艺中被广泛使用，北美本土李子似乎有很大潜力成为一种有价值的北美粮食作物。

Prunus (plant family Rosaceae) is a large diverse genus of the temperate northern hemisphere with about 200 species and includes such economically important species as plums /prunes, peaches, apricots, cherries, and almonds. The North American plum group includes about 13-17 species that are so closely related that they have not established reproductive barriers and frequently hybridize. Because they hybridize so readily, species boundaries cannot easily be delimited and therefore differentiation and classification of North American plum species has long been difficult. The North American plums serve as an interesting model for systematic studies (the study of the kinds and diversity of organisms and the relationships among them) because they are at the interface of phylogenetics (studies of evolutionary relationships among species) and population genetics (studies of patterns of genetic variation among populations of species). This study will therefore not only help to resolve the relationships within a closely related group of species but it will also test the limits of phylogenetic resolution in a closely related group of species. Evolutionarily closely related groups of species that are difficult to distinguish morphologically are amenable to analysis with genetic data. The goals of this research are to resolve the evolutionary relationships among the North American plums using DNA sequence data. By comparing the DNA sequences of multiple accessions of each putative species from throughout their ranges, we can infer how much genetic variation exists within each species and how much genetic differentiation exists between putative species. This research will be important to the academic community as it will serve as a baseline investigation of a very closely related group of species. Many species within the genus Prunus are economically important as ornamentals or food crops (e.g., plums /prunes, peaches, apricots, cherries, and almonds). The Eurasian plums of are those most often used in agriculture but are difficult to grow in many parts of North America because they are not well adapted to environmental conditions or diseases. Native North American plums, the focus of this research, are not cultivated on a large scale, although some species are currently under investigation as potential food crops. Most plum crop species are of hybrid origin from a small number of native Eurasian plums. Because there are more native North American plum species, the potential for improved cultivars through hybridization is greater. In addition to their potential economic importance, several species of North American plums are of conservation concern at the state level. Further, the scrub plum (P. geniculata) is Federally Endangered and restricted to only four counties in central Florida where habitat loss through development is critically endangering its habitat. Thus, understanding the classification and evolutionary history the native North American plums is of economic importance as well as conservation and biological interest. Lastly, this work will be of utility to the agricultural and horticultural communities as Prunus is used extensively in horticulture and there appears to be great potential for native North American plums to become a valuable North American food crop.