Evolution of scaly tree ferns (Cyatheaceae) in Madagascar and adjacent regions

马达加斯加以其丰富的物种、独特的植物群和包括蕨类植物在内的维管植物的高特有率而闻名。大约有50种鳞叶树蕨分布在马达加斯加和邻近的岛屿。它们可以归属于五个形态上不同的组，都属于泛热带属Alsophila。在这个项目中，我们探讨（1）这些假设的群体的单系性，（2）这些群体之间的关系和非马达加斯加种的Alsophila，（3）假定的殖民化事件马达加斯加从非洲或澳大拉西亚，和（4）马达加斯加辐射的一个或多个这些假定的群体。另一个目标是重建马斯卡林特有种（3-5种）的扩散和物种形成历史。这些目标将通过（1）产生四个cpDNA和三个nrDNA标记的核苷酸序列，（2）重建物种水平的进化史，（3）通过电泳分析推断每个进化枝的祖先区域，以及（4）估计分歧时间来实现。现存的树蕨在这一地区的多样性是一个长期的隔离后，分裂的冈瓦纳和/或辐射殖民通过长距离传播从非洲，澳大拉西亚，或新热带地区的结果。树蕨作为低效的长距离扩散者，其化石可以追溯到侏罗纪，是支持或拒绝这些假设的一个注定的模式系统。

Madagascar is renowned for its species richness, distinctiveness of its flora, and high rate of endemism in vascular plants including ferns. About 50 species of scaly tree ferns occur in Madagascar and adjacent islands. They can be ascribed to five morphologically distinct groups all belonging to the pantropical genus Alsophila. In this project, we explore (1) the monophyly of these hypothetical groups, (2) the relationships among these groups and to non-Madagascan species of Alsophila, (3) putative colonization events of Madagascar from Africa or Australasia, and (4) Madagascan radiations of one or more of these putative groups. A further objective is the reconstruction of dispersal and speciation history of the Mascarene endemic species (3-5 spp.). These objectives will be achieved by (1) generating nucleotide sequences of four cpDNA and three nrDNA markers, (2) reconstructing a species level phylogeny, (3) inferring ancestral areas for each clade by biogeographic analysis, and (4) estimating divergence times. The extant tree fern diversity in this region is either the result of a long isolation after the split of Gondwana and / or radiations following colonization via long-distance dispersal from Africa, Australasia, or the Neotropics. Tree ferns as inefficient long distance dispersers with fossils dating back to the Jurassic are a predestined model system to sustain or reject these hypotheses.