Phylogenetics of New World Aneuploid Astragalus: Molecular, Morphological, and Cytogenetic Evidence

9407824桑德森黄芪属豆科开花植物，全世界有2,500多种，是全球范围内快速进化多样化的杰出例子。重建这样一个属的进化关系或系统发育可以为为什么它在生态上如此成功提供线索。然而，与大型属的系统发育分析相关的技术和后勤问题阻碍了在理解黄芪属内的关系方面取得重大进展。一种有希望的方法是识别主要的亚组，建立这些亚组的系统发育地位(无论它们是否为单系)，然后重建它们之间的关系。本研究将评估三种系统发育假说，这些假说涉及黄芪中一个大的推定的单系类群。这一群由分布在新大陆的一系列约500种物种组成，它们都拥有不同于该属其他物种的不寻常的染色体组合(它们是非整倍体)。这三个假设是：(1)所有新大陆非整倍体形成一个不同于稀有的东半球非整倍体和同样罕见的新大陆整倍体的单系群；(2)东半球非整倍体代表着非整倍体染色体条件在进化上独立的起源；(3)新大陆整倍体不是新大陆非整倍体的近亲，而是与东半球物种更近的亲缘关系。核糖体和叶绿体DNA突变差异的证据将从数百个新旧大陆物种中收集，并与染色体计数和形态特征相结合。将努力检测与新旧大陆非整倍体群体起源有关的可靠形态特征。

9407824 Sanderson The flowering plant genus Astragalus, of the legume family, containing upwards of 2500 species worldwide, is a remarkable example of rapid evolutionary diversification on a global scale. Reconstructing the evolutionary relationships or phylogeny within such a genus can provide clues as to why it is so ecologically successful. However, the technical and logistical problems associated with phylogenetic analyses of large genera have prevented significant progress in understanding relationships within Astragalus. One promising approach is to identify major subgroups, establish the phylogenetic status of these (whether they are monophyletic), and then reconstruct their relationships to each other. The present study will evaluate three phylogenetic hypotheses regarding one large putative monophyletic group within Astragalus. This group consists of a series of some 500 species distributed in the New World, which all possess an unusual chromosome complement (they are aneuploids) that differs from the rest of the genus. The three hypotheses are (1) that all New World aneuploids form a monophyletic group distinct from rare Old World aneuploids and equally rare New World euploids; (2) that Old World aneuploids represent evolutionarily independent origins of the aneuploid chromosome condition; and (3) that New World euploids are not the closest relatives of New World aneuploids, rather they are more closely related to Old World species. Evidence from mutational differences in nuclear ribosomal and chloroplast DNA will be gathered from hundreds of New and Old World species, and integrated with chromosome counts and morphological features. Efforts will be made to detect reliable morphological characters associated with the origin of the aneuploid groups in the New and Old World.