Molecular Phylogeny Of Colocasia Schott

Plant molecular phylogeny of eleven species of Colocasia (L.) Schott, micromorphologies of six Colocasia species, and floral organogenesis of Colocasia bicolor, have been studied for the first time. Results are as follows:1. There are some differences in morphology of eleven species of Colocasia. Owing to various environment and individual development, these morphological characteristics can be easily affected and have more variability. Sometimes it is difficult to use these characteristics to identify species in the genus Colocasia Schott because their inflorescences are not easy to observe in mid and high latitude or high altitude areas.2. The general characteristics of leaf epidermis of six Colocasia species under SEM shows that they have some differences in crest, epidermis appendent, stomata and the two poles of guard cell having thicken with "T" type or not, etc. The study of characteristics of six Colocasia species in leaf epidermis under SEM has enriched the systematic data of Colocasia, which will be much significant both in taxonomic research and in discussion of systematic relationships.3. Inferred from the analyses based on ITS DNA region of Colocasia Schott, the phylogenetic relationships within the genus were discussed in the present paper. There is 688-747bp in length of ITS sequence in Colocasia Schott including 278 variable sites and 136 informative sites, which the percentage is 35.19 and 17.22 compared with the whole ITS sequence, respectively. It shows that it is feasible using ITS to discuss the phylogeny relationship in Colocasia Schott. According to the differences of G+C percentage between the out-group of Aolocasia odora and thein-group of Colocasia Schott, which is less than 1%. Aolocasia odora is an ally of Colocasia Schott and was selected as the out-group is appropriate. The monophyly of the whole genus, Colocasia Schott was strongly supported in all the analyses. C. yunnanensis, C. menglaensis and C. gongii are also supported as monophyly in the Colocasia ITS phylogeny tree. C. esculenta and C. gaoligongensis, C. heterochmma and C. bicolor are two monophyletic groups. The percentage G+C, divergence and homology of C. esculenta, C. gongii, C. gaoligongensis and C. yunnanensis indicate they are ally. Though the divergence and homology of C. lihengiae and C. lihengiae var. nigra both indicate they are nearly relatives, they have two base differences in ITS and these two species are different in divergence time in history. Our evidences support that the latter is the variety of the former. C. gigantea is an absolute evolutionary branch in the phylogeny tree of Colocasia Schott, and is the most evolutionary species in the whole genus, while C. esculenta and C. gaoligongensis are primordial groups in the genus. The analyses based on ITS not only make clear relationships among species in this genus but also provide new evidences of some disputed species taxonomically. From a comprehensive view of morphology, geobotany and molecular phylogeny, we consider that Colocasia Schott can be divided into three groups: C. gigantea occupies one group including only one species; C. heterochroma and C. bicolor consist of the second group, and other species are in the third group.4. The spadix of Colocasia bicolor contains unisexual flowers without a perianth. The pistillate flowers are initiated on the basal portion of the inflorescence, and the staminate flowers are initiated on the apical portion. There is a narrow zone between the male flowers and female...