Origin and Evolution of Endemic Asteraceae From the Macaronesian Archipelagos

小行星9707614 得克萨斯大学的罗伯特·詹森博士与外国同事哈维尔·弗朗西斯科·奥尔特加博士和阿诺尔多·桑托斯·格拉博士合作，正在研究马卡罗尼西亚群岛、加那利群岛、马德拉群岛和亚速尔群岛上的菊科向日葵亲属的几个属的植物发生和植物地理学。超过800种植物被描述为这些岛屿特有的（在其他地方找不到），其中25%属于菊科，这表明岛屿之间和单个岛屿上的进化辐射。来自叶绿体和核基因的DNA测序的新证据，来自岛屿物种的样本以及来自非洲和地中海物种的同事提供的疑似相关的集合，将有助于构建系统发育树或谱系，如银菊属，Cheirolophus，Pericallis和Tolpis。在现代专题治疗存在的属，如银菊属，分子证据可以整合与所有物种的形态特征描述，以评估在选择的花和营养功能的物种之间的变化率和模式。的系统发育研究Cheirolophus（族Cardueae），Pericallis（族Senecioneae），Tolpis（族莴苣）将有助于新生的努力，以确定这些大的亚组的向日葵家族在世界范围内的系统发育树结构。 许多相互矛盾或重叠的理论已经被提出来解释Macaronesian群岛特有物种的数量和分布，但没有一个很好的支持系统发育框架来指导进化和迁移的假设，理论可能会继续不受约束。无论是非洲大陆还是地中海地区都是Macaronesia的移民来源，是否可能发生了回移，是否有单个或少数移民辐射成许多新物种，而不是来自大陆来源的多个移民创造了岛屿的多样性，物种形成是否更常发生在岛屿之间，或个别山区岛屿的海拔带之间，所有这些植物地理学的问题都可以在所考虑的几组植物的有力支持的系统发育框架内进行研究。

9707614 Jansen In collaboration with foreign colleagues Drs. Javier Francisco-Ortega and Arnoldo Santos-Guerra, Dr. Robert Jansen of the University of Texas is studying the phylogeny and biogeography of several genera of sunflower relatives, family Asteraceae, on the islands of the Macaronesian archipelago, the Canaries, Madeiras, and Azores. Over 800 species of plants have been described that are endemic to these islands (found nowhere else), and 25% of these belong to the family Asteraceae, which shows instances of evolutionary radiation both among islands and elevationally on single islands. New evidence from DNA sequencing of chloroplast and nuclear genes, from samples of island species and from collections provided by colleagues from African and Mediterranean species suspected to be related, will help construct phylogenetic trees or genealogies for such genera as Argyranthemum, Cheirolophus, Pericallis, and Tolpis. Where modern monographic treatments exist of the genera, such as for Argyranthemum, the molecular evidence can be integrated with morphological characters described for all the species, to assess rates and patterns of change among species in select floral and vegetative features. The phylogenetic studies on Cheirolophus (tribe Cardueae), Pericallis (tribe Senecioneae), and Tolpis (tribe Lactuceae) will contribute to nascent efforts to determine the phylogenetic tree structure for these large subgroups of the sunflower family on a world-wide basis. Numerous conflicting or overlapping theories have been proposed to explain the number and distribution of endemic species on the Macaronesian islands, but without a well supported phylogenetic framework to guide hypotheses about evolution and migration, the theorizing may continue unconstrained. Whether the African mainland or Mediterranean regions have served as sources for migrants to Macaronesia, whether back migration may have occurred, whether single or few migrants radiated into numerous new species as opposed to multiple in troductions from continental sources creating the diversity of the islands, whether speciation has occurred more often between islands or between elevation zones on individual mountainous islands_all these questions of biogeography can be studied within a robustly supported phylogenetic framework of the several groups of plants under consideration.