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

9615437弗洛登斯坦兰科植物是开花植物中最大的一科，估计有25,000种。它在花卉外观上表现出高度的多样性，但这种多样性是相对较少的特征变化的结果。似乎有几个特征反复进化，导致在不相关的类群中产生相似的花形态。因此，尽管科学家们对兰科的分类已经研究了近200年，但对于主要兰科(亚科和部落)内部和之间的关系仍有很大的不确定性。这项研究考察了该科163个代表性属的亲缘关系，重点是大型且分辨不良的石斑亚科，并通过两种方式为该科内的关系问题带来了新的视角：(1)利用来自三个基因组(叶绿体、核和线粒体)的DNA序列数据，这些基因组可能不处于与形态特征相同的选择压力下；(2)通过对花药和花粉结构的发育研究，重新评估传统上强调的花特征。肯特州立大学的约翰·弗洛伊登斯坦博士在第一个项目中与英国皇家植物园的马克·蔡斯博士合作，在第二个项目中与哥本哈根大学的芬恩·拉斯穆森博士合作。这项研究的意义是多方面的。它将提供代表该科多样性的同一属组的几个数据集，产生迄今为止为该科建立分类所依据的最大信息量。一些类群，如经济上重要的香草，一直很难归类，因为它们与其他类群几乎没有共同的高级特征；分子数据在理解它们的关系方面将特别重要。这种关系模式将形成一个迫切需要的框架，以便在家庭的较低级别进行进一步研究，并将有可能解决以下问题：传统上使用的花卉字符有多可靠？什么是被推定为标志物种丰富谱系的“关键”创新？不同物种丰富的谱系是否共享独立派生的相同创新，或者它们以不同的方式取得了成功？骨痂在家族中进化了多少次？除了阐明兰花之间的进化模式外，这些问题的答案也与其他植物群的进化研究有关。更具普遍意义的是在家族一级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.