Cladistics of Orchidaceae and Critical Anther Characters: Evidence from Molecular, Developmental and Morphological Investigations

兰科是最大的开花植物科，估计有25000种。它在花的外观上表现出高度的多样性，然而这种多样性是在相对较少的特征上变化的结果。似乎有几个特征反复进化，导致在不相关的群体中有相似的花形态。因此，尽管科学家们已经对这个科进行了近200年的分类，但关于主要兰花群（亚科和部落）内部和之间的关系仍然存在很大的不确定性。本研究考察了来自整个家族的163个代表性属的关系，强调了庞大而难以解决的Epidendroideae亚科，并从两个方面为家族内的关系问题带来了新的视角：(1)利用来自三个基因组（质体，核和线粒体）的DNA序列数据，这些数据可能不受形态特征相同的选择力的影响；(2)通过花药和花粉结构的发育研究，重新评价传统上强调的花性状。肯特州立大学的约翰·弗罗伊登斯坦博士与英国皇家植物园的马克·蔡斯博士在第一个项目中合作，与哥本哈根大学的芬恩·拉斯穆森博士在第二个项目中合作。这项研究的意义是多方面的。它将为代表该科多样性的同一组属提供若干数据集，从而产生迄今为止为该科建立分类所依据的最大信息量。有些群体，比如经济上重要的香草族，很难定位，因为它们与其他群体共享的高级角色很少；分子数据对于理解它们之间的关系尤为重要。这种关系模式将为进一步在较低层次的家庭中进行研究提供一个急需的框架，并将使解决以下问题成为可能：传统使用的花卉特征有多可靠？什么被认为是标志着物种丰富谱系的“关键”创新？不同的物种丰富的谱系是否共享独立衍生的相同创新，或者它们以不同的方式取得成功？附生病在家族中进化了多少次？除了阐明兰花的进化模式外，这些问题的答案也与其他植物群的进化研究有关。此外，更普遍的相关性将是在家庭水平上比较来自三个基因组的数据集之间的模式，以及开发线粒体DNA序列作为开花植物系统发育研究的工具。

9615437 Freudenstein The Orchidaceae is the largest family of flowering plants with an estimated 25,000 species. It exhibits a high degree of diversity in floral appearance, yet this diversity is the result of change in a comparatively small number of features. It appears that several characteristics have evolved repeatedly, leading to similar floral morphologies in unrelated groups. Hence, although scientists have been working on classifications of the family for nearly 200 years, there is still a great deal of uncertainty about relationships within and among the major orchid groups (subfamilies and tribes). This study examines the relationships of 163 representative genera from across the family, emphasizing the large and poorly resolved subfamily Epidendroideae, and brings a fresh perspective to the question of relationships within the family in two ways: (1) by utilizing DNA sequence data from three genomes (plastid, nuclear, and mitochondrial) that are presumably not under the same selective forces as are morphological characters; and (2) by re-evaluating the traditionally emphasized floral characters with developmental studies of the anther and pollen structures. Dr. John Freudenstein of Kent State University is collaborating with Dr. Mark Chase at England's Royal Botanic Gardens-Kew in the first project and with Dr. Finn Rasmussen at the University of Copenhagen in the second. The significance of this study is several-fold. It will provide several data sets for the same set of genera representing the diversity in the family, yielding by far the maximal amount of information to date on which to build a classification for the family. Some groups, such as the economically important Vanilla, have been difficult to place because they share few advanced characters with other groups; the molecular data will be especially important in understanding their relationships. The pattern of relationships will form a much-needed framework for further studies at lower levels in the family, and will make it possible to address the following questions: How reliable are the traditionally used floral characters? What are presumed "key" innovations that mark species-rich lineages? Do different species-rich lineages share the same innovations that were derived independently, or have they achieved success in different ways? How many times has epiphytism evolved in the family? In addition to elucidating evolutionary patterns among orchids, answers to these questions are relevant to studies of evolution in other plant groups. Also of more general relevance will be the comparison of patterns among data sets from three genomes at the family level and the development of mitochondrial DNA sequences as a tool for phylogenetic studies in flowering plants.