论山毛榉科植物的系统发育

本文运用分支分类学方法，对山毛榉科植物进行了系统发育的分析。山毛榉科作为单元发生群包括柯属、锥属、粟属、三棱栎属、水青冈属和栎属。桦木科和南山毛榉属被选择作为外类群。对大量的性状进行评估之后，选择了25对性状作为建立数据矩阵的基本资料。性状极化以外类群比较为主，同时也采用了化石证据和通行的形态演化的基本原则。数据矩阵由7个分类群、2个外类群和25个性状组成。采用最大同步法、演化极端结合法和综合分析法对该数据矩阵进行了分析。在得到的3个树状分支图中按照最简约的原则，选出演化长度最短的谱系分支图作为本文讨论山毛榉科属间的系统演化关系的基础。关于山毛榉科植物的系统发育，作者的观点如下：(A)现存的山毛榉科的6个属形成了4条平行进化的分支路线，它们分别被处理作4个亚科，即：栗亚科，三棱栎亚科，水青冈亚科和栎亚科；(B)平行进化是山毛榉科植物系统发育过程中的主要形式。生殖过程中的一些特征，如：果实第二年成熟，胚珠通常败育等，是影响山毛榉科植物属间基因交流的主要原因。在现存的山毛榉科植物中，柯属是最原始的类群。三棱栎属和锥属的起源也较早，而栗属、水青冈属和栎属是特化的类群。

ON THE PHYLOGENY OF THE FAGACEAE

A cladistic analysis of the genera in the family Fagaceae is made in the present paper. As a monophyletic group, the family Fagaceae includes 6 genera, namely, Lithocarpus,Castanopsis,Castanea,Trigonobalanus,Fagus and Quercus. The Betulaceae and Nothofa-gaceae were selected for outgroup comparison after a careful consideration. Twenty five informative characters had been used in this study. Three principles;outgroup comparison,fossil evidence and generally accepted view points of morphological evolution, were used for polarization of the characters. A data matrix was constructed by 7 ingroups,2 outgroups and 25 characters. The data matrix was analysed with the Maximal Same Step Method, Group Union Method and the Synthetic Method. Three cladograms were constructed and a parsimonious cladogram (Lenth=75) was used as the bases in discussing the intergeneric systematic relationships in Fagaceae. In the Fagaceae,the first differentiated group might be the extinct common ancester of the extant genera Lithocarpus, Castanopsis and Castanea. They are reasonably with the distinct characters: mixed inflorescence or androgynous and the female flowers with stamin-odes. Among the three genera, Lithocarpus was differentiated earlier than the others and it remains more primitive (entire leaves; smaller diameter of vesseles; scanty tylose;cupule scaly appendages; mixed inflorescence and the female flowers with well developed stamens in some species) ,Castanopsis is closely related to,but more primitive than Castanea. As in a clade group, the genus Trigonobalanus orginated apparently later than the ancester of Lithocarpus,Castanopsis and Castanea. Fossil evidence suggests that this genus originated as early as in the Paleocene to Eocene. And some characters, for example, leaf with glandular peltate trichomes,chromosome number 2n = 44,are only appeared in Trigonobalanus. Three species in this genus are disjunctly distributed in tropical Asia and South America, this genus is considered as both an isolated and primitive taxon in the Fagaceae,and it is also probably paraphyletic with the subfamily or tribe categories in this family. As shown in cladograms 1 and 2, the genus Fagus forms an isolated clade which consists of a relatively advanced taxon in the Fagaceae (with fiber tracheid and the reduction of the inner integument). In three cladograms,the clade of Quercus is the most advanced one,which is consistent with the current view-point about the systematic position of the genus Quercus and the concept of Quercus (s. 1. ) in Fagaceae. The following conclusions may be reached by the author: (1) The six genera in the Fagaceae evolved in four parallel lines phylogenetically, so they could be treated as four independent subfamilies, namely Castaneoideae, Trigonobalanoideae, Fagoideae and Quercoideae; ( 2 ) Parallel evolution is the main form in the phylogeny of the Fagaceae, some characters of the reproductive cycle, for example, fruit becoming ripe in the next year and the abortion of ovules etc. are the main factors which affect the gene flow among the genera in the Fagaceae; (3) In the Fagaceae,Lithocarpus is a primitive genus,and Trigonobalanus and Cas-tanopsis both are also relatively primitive, but Castanea, Fagus and Quercus are relatively advanced.