Dissertation Research: Evolution of Dendrochilum Orchids on Mt. Kinabalu Examined in a Phylogenetic Context

研究生托德·巴克曼在德克萨斯大学导师贝丽尔·辛普森的指导下，正在研究东南亚植物进化和分布的一个有趣问题。该项目的重点是兰花属Dendrochilum和Eurybrachium的20-30种，它们主要分布在婆罗洲的大岛上，仅在Kinabalu山上就有许多。野外采集将增加植物标本室的资料，以便对营养和花的性状进行详细的形态学研究；实地工作利用了约翰·比曼教授及其马来西亚和印度尼西亚同事的植物区系清查活动。此外，核和叶绿体基因的分子（DNA）分析将为测量物种之间的突变差异和推断系统发育关系提供新的数据。在苏门答腊岛、爪哇岛和苏拉威西岛以及菲律宾和马来西亚的相关种群也将进行系统发育比较研究。一个强大的物种系统发育将测试两个相互竞争的假设，这些附生兰花的起源。一种假说认为婆罗洲的适应性辐射来自单一祖先的引入；第二种假说认为，婆罗洲周围的不同岛屿引入了多种物种。将传统的形态特征与DNA测序的新分子数据相结合，有望为植物分类提供更可靠的依据，并对物种间的系统发育（系谱）关系进行强有力的推断。有了这种系统发育，就可以分析历史生物地理学的模式（迁移、适应性辐射、物种形成）。巴克曼和辛普森对兰花石斛的研究是这种恢复活力的植物系统学的另一个例子。＊＊＊

9623638 Simpson Graduate student Todd Barkman, with direction from adviser Beryl Simpson at the University of Texas, is studying an interesting problem in plant evolution and distribution in Southeast Asia. The focus of the project is the orchid genus Dendrochilum and the 20-30 species of subsection Eurybrachium that occur mostly on the large island of Borneo, with many on Mt. Kinabalu alone. Field collections will augment herbarium materials to enable detailed morphological study of vegetative and floral characters; field work capitalizes on the floristic inventory activities of Prof. John Beaman and his Malaysian and Indonesian colleagues. In addition, molecular (DNA) analyses of nuclear and chloroplast genes will add new data for measuring mutational differences between the species and for inferring phylogenetic relationships. Related groups on the islands of Sumatra, Java, and Sulawesi, and in the Philippines and Malaysia will also be studied for phylogenetic comparisons. A robust phylogeny of the species will test two competing hypotheses for the origin of these epiphytic orchids. One hypothesis claims adaptive radiation on Borneo from a single ancestral introduction; the second hypothesis claims multiple introductions from different islands around Borneo. %%% The integration of traditional morphological characters with new molecular data from DNA sequencing promises a more reliable taxonomy of plants and the robust inference of phylogenetic (genealogical) relationships among species. With this phylogeny in place, patterns of historical biogeography (migration, adaptive radiations, speciation) can be analyzed. Barkman and Simpson's study of Dendrochilum orchids is one further example of this rejuvenated plant systematics. ***