Systematic study on Gondwanan plant, Podocarpus (Podocarpaceae)

罗汉松科由17属和约17属组成。125种（Page，1990），主要分布于南半球。罗汉松科在生态习性上是多样化的，它的亚科分类包括科的界限一直是有问题的。本研究旨在构建叶绿体编码atpB、matK和rbcL基因的序列数据库，以重建该科的分子系统学，并利用该系统学来解决Podocarpus属的界限问题，即，本文研究了竹柏属、非洲竹柏属、纳加属、十果竹柏属、Retrophyllum属、Parasitaxus属、Prumnopytis属和Sundacarpus属的系统发育关系。竹柏属与Afrocarpus、Nageia、Decussocarpus和Retrophyllum属为单系，而Parasitaxus、Prumnopytis和Sundacarpus与该属无关。后者位于该科的基部分支上，与Lagarostrobos、Lepidothamnus、Phyllodadus和Halocarpus等属构成单系群。de Laubenfels（1969，1985）提出的竹柏属的单属分类得到了分子系统学的有力支持。气孔器上有无Florin环和叶片形态等形态特征可作为植物发生的信息特征。研究结果表明，在白垩纪（冈瓦纳大陆解体之前）之前，竹柏属的物种已经演化为两个亚属，并且每个亚属的物种在南半球的每个地区都是独立演化的。

The family Podocarpaceae is composed with 17 genera and ca. 125 species (Page, 1990), and is mainly distributed in the southern hemisphere. The family Podocarpaceae is diversified in their ecological habit, and its infrafamilial classification including the circumscription of the family has been problematic. This study aims to construct a sequence database for the chloroplast encoded atpB, matK and rbcL genes in order to reconstruct a molecular phylogeny for the family and to use this phylogeny to address the circumscription of the genus Podocarpus, I.e., phylogenetic relationships among the genera of Podocarpus sensu stricto, Afrocarpus, Nageia, Decussocarpus, Retrophyllum, Parasitaxus, Prumnopytis and Sundacarpus. The genus Podocarpus is monophyletic with genera of Afrocarpus, Nageia, Decussocarpus and Retrophyllum, however, Parasitaxus, Prumnopytis and Sundacarpus are unrelated to the genus. The latter group is located on the basal clade within the family and makes a monophyletic group with genera of Lagarostrobos, Lepidothamnus, Phyllodadus, and Halocarpus. Infrageneric classification of the genus Podocarpus suggested by de Laubenfels (1969, 1985) was strongly supported by the molecular phylogeny. Morphological characteristics such as presence or absence of Florin ring on stomata and morphology of leaves were revealed to be informative characteristics for the phylogeny. The present result indicates that species of Podocarpus had already evolved into the two subgenera until Cretaceous (prior to breakup of Gondwanaland), and species of each subgenus was independently evolved in each area of the southern hemisphere.