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

冰草属（Wheatgrass genus）与小麦、大麦和黑麦同属一个类群，该属内的禾本科植物适应了不同的气候和生境，是谷类和牧草育种的宝贵遗传资源，也是研究进化、分类和物种形成的优良类群。所有冰草都至少由两套不同的染色体组成，大多数物种具有StY和StH染色体组合。约有50个物种具有StH组合。St基因组来自Pseudoroegneria属的祖先物种，H来自野生大麦。关于这一群体的一个争论是，不同的StH物种是否是由一对亲本，一个假鹅观草属物种和一个野生大麦之间的古老杂交产生的，然后分化成许多物种（单一起源），或者不同的StH物种是由不同的亲本在不同的时间和地点之间的杂交产生的（多个起源）。以前的一些研究似乎支持多起源的假设，但没有提供有力的支持。我们将测试是否StH基因组组是多个起源。如果是这样的话，我们将看看我们是否可以确定哪些StH物种来自哪些假鹅观草（St）和野生大麦（H）物种使用DNA数据。八种南美洲本土的Escherichus物种与其他地区的Escherichus物种没有任何明显的联系。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，将该属的StH种分为7个组。我们将使用DNA序列数据来测试具有相似形态的物种是否在遗传上彼此相关。 这项研究的结果将提供一个系统发育框架，研究的进化过程，有助于形态的复杂性的埃克塞特。这些发现也具有农学相关性，因为许多农业上有用的物种在Escherichus。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际和理论意义。

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.