杉科植物的系统发育分析

本文以形态学为依据,参考其他学科的研究成果,用分支分类方法并结合表征分类方法探讨了杉科植物的系统演化关系,提出了新的分类系统。在分支分类中,金松科被选作外类群。主要根据外类群比较原则、化石原则和一般的演化规律,确定了性状的祖征和衍征,采用最大同步法、综合分析法、演化极端结合法及最小平行进化法共四种方法进行分支分析,选择最简约的分支图作为本文讨论基础。在表征分类中,选取59个性状,利用距离系数和类平均法,对金松属和杉科各属进行了聚类运算,得出表征图。综合两种分析结果,主要结论如下:(1)属间关系:柳杉属是现存杉科植物中最原始的类群。水松属和落羽杉属关系密切,二者与柳杉属近缘。巨杉属和北美红杉属关系密切,是中级进化水平的类群。水杉属与巨杉属和北美红杉属的亲缘关系相对较近。杉木属、密叶杉属和台湾杉属关系密切,是杉科植物中的高级进化类群,其中又以台湾杉属演化水平最高。(2)系统排列:支持金松科的成立,将杉科分成5族,即柳杉族(仅含柳杉属)、落羽杉族(含水松属、落羽杉属)、北美红杉族(含巨杉属、北美红杉属)、水杉族(仅含水杉属)和杉木族(含杉木属、密叶杉属及台湾杉属)。

PHYLOGENETIC ANALYSIS OF THE FAMILYTAXODIACEAE

In the present paper, both cladistic analysis and phenetic analysis were conducted to evaluate the phylogenetic relationships of the Taxodiaceae based on an extensive literature review and study of herbarium. In the cladistic analysis, the Sciadopityaceae was chosen as outgroup. The polarity of characters was determined mainly according to outgroup comparison, fossil evidence and generally accepted viewpoints of morphological evolution. By the result of compatibility analysis , character 2 (leaf type) , which possessed a much higher coefficient than others whether or not its polarity was altered,was deleted. Finally, a data matrix consisting of all the extant nine genera and 24 characters was analyzed using Maximal Same Step Method, Synthetic Method, Evolutionary Extremal Aggregation Method and Minimal Parallel Evolutionary Method, and four cladograms were generated, of which only the most parsimonious one (Fig. 1) was presented for discussion. The cladogram shows that the Taxodiaceae are assorted along five lines of evolution; 1) Metasequoia; 2 ) Sequoiadendron, Sequoia; 3 ) Cryptameria; 4 ) Glyptostrobus and Tax-odium ; 5) Cunninghamia, Athrotaxis and Taiwania. Ten genera (including Sciadopitys) and 59 characters were used in the phenetic analysis. The phenogram (Fig. 2) indicates that Sciadopitys is a very distinct group with remote affinity to the other genera, and the Taxodiaceae are divided into four groups 1) Sequoia, Sequoiadendron; 2) Athrotaxis, Cunninghamia and Tahvania; 3) Cryptomeria, Glyptostrobus and Taxodium; 4) Metasequoia. Based primarily on the result of cladistics, with reference to that of phenetics, the main conclusions were drawn as follows:(1) Generic relationships; Cryptomeria should be con- sidered the most primitive genus in the extant groups of the Taxodiaceae. Glyptostrobus and Taxodium, close to Cryptomeria, are sister taxa and relatively primitive groups. Se-quoiadendron and Sequoia are closely related and intermediate advanced. Metasequoia is a more or less isolated taxon, relatively close to Sequaiadendron and Sequoia . Cunninghamia ?Athrotaxis and Tahuania might represent a single lineage and form a very advanced group, of which Tahuania may be the most specialized. (2) Systematic treatments ?The authors support the viewpoint that Sciadopitys should be treated as an independent family, and suggest that the Taxodiaceae should be divided into five tribes. Systematic arrangements are as follows: Taxodiaceae Warming Trib. 1. Cryptomerieae Vierhapper Gen. 5. Sequoia Endl. Gen. 1. Cryptomeria D. Don Trib. 4. Metasequoieae Pilger et Melchior Trib. 2. Taxodieae Benth. et Hook. Gen. 6. Metasequoia Miki ex Hu et Cheng Gen. 2. Glyptostrobus Endl. Trib. 5. Cunninghamieae Zucc. Gen. 3. Taxodium Rich. Gen. 7, Cunninghamia R. Br. Trib. 3. Sequoieae Wettstein Gen. 8. Athrotaxis D. Don Gen. 4. Sequoiadendron Buchholz Gen. 9. Tarwania Hayata