A Systematic Investigation of the South African Holoparasitic Genus Hyobanche L. (Orobanchaceae)

沃尔夫寄生植物是在被子植物的几个谱系中已知的一种寄生植物，它们已经失去了所有的光合作用，通过吸器(通常是根)连接从附近的植物吸收营养而生存。Hyobance(属于Orobanchaceae科)就是这样一个类群，一个由大约8个物种组成的小属，原产于南非，被认为与光合作用属Harveya有亲缘关系。关于Hyobance的物种定界、丰度、寄主协会和授粉，有相当大的混乱，这在现场还没有得到任何详细的研究。俄亥俄州立大学的Andrea Wolfe博士正在研究这类植物的系统学、进化和生物学，通过将野外收集和观察与实验室的形态和DNA测序工作相结合，为系统发育和种群遗传学分析获得新的特征。由于该属很小，而且分布限于狭小的地理区域，因此计划从所有物种的种群中对许多个体进行彻底抽样。结合形态特征，核基因和叶绿体基因标记有望为物种的系统发育解析提供足够的特征。该属的分类专著预计将作为调查的成果之一，其中将包括详细的地理分布，以帮助保护工作。该项目的一个有价值的组成部分是对叶绿体光合作用基因rbcL的DNA序列和侧翼区域进行详细的分子研究，初步数据表明，该基因在这些植物中突变为一个无功能的“假基因”。Hyobance提供了一个极好的系统，可以在系统发育的背景下研究光合作用丧失后假基因的形成模式和速度。

0089640Wolfe Parasitic plants, ones which have lost all photosynthetic ability and exist by absorbing nutrients through haustorial (usually root) connections from other nearby plants, are known in several lineages of angiosperms. Hyobanche (in the family Orobanchaceae) is one such group, a small genus of eight or so species native to southern Africa, and thought to be related to the photosynthetic genus Harveya. There is considerable confusion regarding species delimitation, abundance, host associations, and pollination for Hyobanche, which has not been studied in the field in any detail. Dr. Andrea Wolfe of Ohio State University is studying the systematics, evolution, and biology of this group of plants, by combining field collecting and observation with laboratory work on morphology and DNA sequencing to acquire new characters for phylogenetic and population-genetic analyses. Because the genus is small and is restricted in distribution to a narrow geographic region, a thorough sampling of many individuals from populations of all the species is planned. Nuclear and chloroplast gene markers are expected to provide sufficient characters for robust phylogenetic resolution of the species, in combination with morphological features. A taxonomic monograph of the genus is projected as one product of the investigation, which will include detailed geographical distributions to aid in conservation efforts. A valuable component of the project is a detailed molecular investigation of the DNA sequences and flanking regions for the chloroplast photosynthetic gene rbcL, which preliminary data suggest to be mutated into a nonfunctional "pseudogene" in these plants. Hyobanche offers an excellent system for examining in a phylogenetic context the pattern and rate of pseudogene formation following the loss of photosynthesis.