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

[407824]桑德森豆科开花植物黄芪属，全世界有2500种以上，是全球范围内快速进化多样化的一个显著例子。在这样一个属中重建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，与大属系统发育分析相关的技术和后勤问题阻碍了在了解黄芪内关系方面取得重大进展。一种有希望的方法是确定主要的亚群，建立这些亚群的系统发育状态（是否为单系），然后重建它们彼此之间的关系。本研究将评估关于黄芪中一个大的假定的单系群的三个系统发育假说。这个群体由一系列分布在新大陆的大约500个物种组成，它们都具有不同于该属其他物种的不寻常的染色体补体（它们是非整倍体）。这三种假说是：(1)所有的新大陆非整倍体形成一个单系群体，与罕见的旧大陆非整倍体和同样罕见的新大陆整倍体不同；(2)旧大陆非整倍体代表了非整倍体染色体状况在进化上独立的起源；(3)新世界整倍体不是新世界非整倍体的近亲，而与旧大陆物种的亲缘关系更近。来自核糖体和叶绿体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相关的可靠形态学特征。

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.