Integrated Study on Evolution of genus Nicotiana (Solanaceae)

点击翻译按钮获取中文摘要

In this project of the study of taxonomy and biogeography, we have challenged a new approach. Thus far, studies of these fields usually treated many taxa of plants at once, while we focused on a representative group of plants and analyzed the evolutionary mechanism of division of speciation and the change of the distribution. We chose the wild-type plants of the genus Nicotiana as the object of our new approach. The genus Nicotiana belongs to Solanaceae and contains about 70 species. The natural distribution of Nicotiana is limited to Southern Hemisphere. 37 species of this genus occur in South America, 20 species in Australia, and a species in Africa. We investigated wild-type species of the genus Nicotiana in Bolivia and Argentina in South America and Australia, New Caledonia, and New Zealand in Oceania. First, as the result of taxonomy we discovered a novel species of the genus Nicotiana in South America. We analyze this plant using molecular phylogenetic and physiological methods. Secondly, we analyzed the change of distribution of some ten species of this genus using the biogeographical method. The result of this analysis is that at least two species, Nicotiana acaulis and N.Ikawakamii has been on the verge of extinction. Thirdly, we have obtained the phylogenetic results that show the origin of tobacco plants (Nicotiana tabacum). N.tabacum is thought to be amphidiploid plants. Although many studies exhibited that the maternal species of N.tabacum is N.sylvestris, the paternal species is unknown. Our analysis indicated that the plants of the paternal species might have been extinct. Research has still been attached to the start just. The further analysis is required in order to confirm these results.