Dissertation Research: Biosystematics and Evolution of the Genus Brachylaena R. Brown (Comlpositae)

Brachylaena（菊科）是一个木本雌雄异株的十三个属 种;它不同于菊科的其他成员， 被认为代表了一个单系组合。 五 Brachylaena的物种是马达加斯加特有的， 马斯卡林群岛，而8种仅限于 非洲大陆。 PI建议测试一些 马达加斯加植物群的起源和亲缘关系 Brachylaena作为一个例子。 该属分布于 分布在两个地区，广泛分布在马达加斯加岛， 暗示着古老的亲缘关系 几个分类学问题， 由于过渡形态学形式已经在 属，因此，建议初步表型分析 以确定群体的界限。 组 然后将从该分析中获得的数据进行比较 通过遗传学方法来确定基因变异， 在各个物种的种群中， 该属物种之间的遗传差异。 只有两 染色体计数已经为属，但它似乎 从这些中，至少一个物种是四倍体。 在 除了表型学和电泳， 叶绿体DNA的限制性位点数据将在 以产生该属的系统发育假说。 这 将与形态学生成的分支图进行比较。 的 Brachylaena的分布，某些物种仅限于 非洲大陆和马达加斯加特有的其他地方， 使我们有可能讨论这个群体的演变， 这两个地区的背景并将其与已知的地质联系起来 事件 此外，生物学和分布的方面， 该属（即，木本，雌雄异株和热带）使其成为一个 一个有趣而重要的群体， 种群内和种群间的差异。

Brachylaena (Compositae) is a woody, dioecious genus of thirteen species; it is distinct from other members of the Compositae and is considered to represent a monophyletic assemblage. Five of the species of Brachylaena are endemic to Madagascar and the Mascarene Islands while eight species are confined to the continent of Africa. The PIs propose to test some of the proposed origins and affinities of the Madagascar Flora using Brachylaena as an exemplar. The genus is distributed between the two regions and it is widespread on the Island of Madagascar, suggesting an ancient affinity. Several taxonomic problems such as intergrading morphological forms have been recognized in the genus therefore, it is proposed that an initial phenetic analysis be carried out to establish the limits of the groups. The groups obtained from this analysis will then be compared electrophoretically to determine the genetic variation within and among populations of individual species and to estimate the genetic divergence among species of the genus. Only two chromosome counts have been made for the genus but it appears from these that at least one of the species is tetraploid. In addition to phenetics and electrophoresis, an analysis of restriction site data from chloroplast DNA will be undertaken in order to produce a phylogenetic hypothesis for the genus. This will be compared to a cladogram generated from morphology. The distribution of Brachylaena, with certain species restricted to the continent of Africa and others endemic to Madagascar, will make it possible to discuss the evolution of this group in the context of the two regions and to relate this to known geological events. Furthermore, aspects of the biology and distribution of this genus (i.e., woody, dioecious and tropical) make it an interesting and important group in which to study genetic variation within and among populations.