Origin and Evolution of Endemic Asteraceae From the Macaronesian Archipelagos

9707614 Jansen与外国同事Jille Francisco-Ortega博士和Arnoldo Santos-Guera博士合作，德克萨斯大学的Robert Jansen博士正在研究马卡洛尼亚群岛、加那利群岛、马德拉斯群岛和亚速尔群岛几个属的向日葵近缘植物菊科的系统发育和生物地理。已有超过800种植物被描述为这些岛屿特有的物种(在其他地方找不到)，其中25%属于菊科植物，这表明在岛屿之间和在单个岛屿上都存在进化辐射的实例。来自叶绿体和核基因的DNA测序、来自岛屿物种的样本以及来自非洲和地中海被怀疑有亲缘关系的物种的同事提供的收集的新证据，将有助于构建Argyranhemum、Cheiroopus、Pericallis和Tolpis等属的系统发育树或系谱。如果存在对该属的现代专题性处理，例如对Argyranhemum，分子证据可以与描述所有物种的形态特征相结合，以评估在选定的花卉和营养特征中物种之间的变化率和模式。对Cheiroopus(Cardueae族)、Pericallis(Senecioneae族)和Tolpis(Lactuceae族)的系统发育研究将有助于在世界范围内确定向日葵家族这些大亚类的系统发育树结构。许多相互矛盾或重叠的理论被提出来解释马卡洛尼群岛特有物种的数量和分布，但如果没有一个得到很好支持的系统发育框架来指导关于进化和迁徙的假说，理论可能会继续下去，不受限制。非洲大陆或地中海地区是否曾是马卡罗尼亚群岛移民的来源地，是否发生了回迁，单个或少数几个移民辐射形成了无数新物种，而不是来自大陆的多个物种引进创造了岛屿的多样性，岛屿之间或个别山区岛屿的海拔带之间更经常发生物种形成--所有这些生物地理学问题都可以在所审议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.