Phylogenetic relationship and origin of allopolyploid StH geonomic species in genus elymus

麦草属与小麦、大麦和黑麦属于同一类群，该属的禾本科植物适应各种气候和生境，是谷物和饲料育种的宝贵遗传资源，也是进化、分类学和物种形成研究的优秀类群。所有的小麦草都由至少两组不同的染色体组成，大多数品种都有StY和StH染色体组合。有StH组合的物种约有50种。其中St基因组来自于原属Pseudoroegneria， H基因组来自于野生大麦。关于这一群体的一个争论是，不同的StH物种是由一对亲本、一种Pseudoroegneria物种和一种野生大麦之间的古代杂交产生的，然后分化成多个物种（单一起源），还是不同的StH物种是由不同时间和地点的不同对亲本杂交产生的（多重起源）。以前的一些研究似乎支持多起源假说，但没有提供强有力的支持。我们将测试StH基因组组是否有多个起源。如果是这样，我们将研究我们是否可以利用DNA数据确定哪个H种来自哪个假芽孢菌（St）和野生大麦(H)种。8种南美本土石斛属植物与其他地区石斛属植物没有明显的联系。最有可能的联系是北美或新西兰。我们将研究这种联系是否存在。根据形态特征，将蕨类植物分为7个类群。我们将使用DNA序列数据来测试具有相似形态的物种是否彼此具有遗传相关性。这项研究的结果将为研究进化过程提供一个系统发育框架，这些进化过程促成了羊草的形态复杂性。这些发现也具有农艺相关性，因为许多农业上有用的物种在羊草。鉴于它们在种质改良中的潜在重要性，了解这些物种的起源和关系具有实践和理论意义。

Wheatgrass genus Elymus is within the same group as wheat, barley and rye, and Grasses within this genus have adapted to various climates and habitats, making them valuable genetic resources for cereal and forage breeding as well as an excellent group for research in evolution, taxonomy, and speciation. All wheatgrasses are made up by at least two different sets of chromosomes with most species having StY and StH chromosome combination. There are about 50 species with StH combination. The St genome comes from ancestor species in genus Pseudoroegneria and H from wild barley. One debate on this group has been whether different StH species arose by an ancient cross between the one pair of parents, a Pseudoroegneria species and a wild barley and then differentiated into a number of species (single origin), or different StH species arose by crosses between different pairs of the parents at different times and places (multiple origins). Some previous studies seem to favor the hypothesis of a multiple origin, but did not provide strong support. We will test whether the StH genome group is multiple origins. If so, we will look at whether we can identify which StH species comes from which Pseudoroegneria (St) and wild barley (H) species using DNA data. Eight South American native Elymus species do not have any obvious connections to Elymus species in other areas. The most probable connection would be with North America or New Zealand. We will examine whether such connections exist. On the basis of morphological traits, the StH species in Elymus were classified into seven sections. We will use DNA sequence data to test whether the species with similar morphology are genetically related to each other.     The outcome of this study will provide a phylogenetic framework for studying the evolutionary processes that have contributed to the morphological complexity of the Elymus. Such findings also have agronomic relevance because of the many agriculturally useful species in Elymus. Given their potential importance in germplasm improvement, understanding of the origin and relationships of these species are of both practical and theoretical interest.