裸藻类植物的分支系统学研究

CLADISTIC ANALYSIS OF EUGLENOIDS

本文选取了裸藻类的33个属级分类单位,以及它们的35个性状,利用分支系统学的原理和方法,对性状的演化极性进行了分析,同时对性状间的极性关系进行了和谐性分析,使性状间极性关系处在较为合理的状态,然后建立了分支分析的数据矩阵。应用徐克学建立的“演化极端结合法”进行微机运算,得简约系数远小于1(0.2159)的分支谱系图。根据分支谱系图对裸藻类的系统发育关系进行了探讨,并与已有的关于裸藻类分类系统和演化假设进行了比较。在此基础上按照裸藻类的亲缘关系及单系原则,对裸藻类的分类等级进行了划分,初步提出了建立1门1纲5目的分类系统。按照在分支谱系中的演化地位,认为裸藻属的5个亚属,明显地都应是独立的属。同时对裸藻类的共生起源与演化的关系也进行了讨论。

A study on phylogenetic relationships in euglenoids is made using the principles of cladistic analysis. In the analysis, 33 genera (i. e. OTUs) of euglenoids were selected and 35 informative characters were used. Three criteria, 'outgroup comparison', 'commonality principle' and 'principle of character correlation', were used in the polarity determination of character states. The sister group of euglenoids ought to be Kinetoplastids in protozoan on the basis of the flagellate structure and molecular biological evidences. Because the euglenoid fossil evidence is inadequate and such fossils,even present, have a very simple ontogenetic process, 'fossil evidence' and 'recapitulation law' are not used to determine primitiveness. A data matrix was constructed by the 33 OTUs and 35 characters . The data matrix was analysed with 'evolutionary extremal aggregation method'. A reasonable parsimonious cladogram (lenth=251, parsimonious coefficient = 0. 2159, was constructed and used as a basis for discuussing the phylogenetics of euglenoids. In the cladogram, the euglenoids may be divided into five large groups . The cladistic points 51 and 48 are the most primitive euglenoids, which are phagotrophic, colourless euglenoids and in closely related to Kinetoplastids in protozoan; the point 62 is green euglenoids, which probably evolved by endosymbiosis between phagotrophic colourless euglenoids and green algae; the point 58 is the most complex group, containing advanced green euglenoids in evolution and saprophytic colourless euglenoids which probably evolved from green euglenoids by losing their chloroplasts; the point 37 is a rare group, parasitic euglenoids with many flagella. According to the phylogeny of euglenoids in the cladogram, a classification which includes one division, one class and five orders may be proposed. It is obviously different from the former systems set up by other biologists. Five subgenera of Euglena may be identified as independent genera on the basis of their characters and evolutionary lines in the cladogram.