Phylogenetic Position And Recovery Assessment Of Metasequoia Glyptostroboides

Biodiversity loss led by human activities is a global environmental problem. An unknown but large number of species are already extinct, while many others have reduced population sizes that put them at risk. The main aim of conservation is to recover threatened or endangered species to the extent they can sustain without human being's assistance. However, the main concern of the conservation focuses on the recovery of the numbers of the threatened and endangered species, and few effort has been on their genetic variation, which is critical to cope with environmental changes.Dawn Redwood (Metasequoia glyptostroboides), a living fossil, is an important endangered plant species with a limited distribution around the borders of Hubei Province, Hunan Province and Chongqing Municipality in China. Great conservation efforts, including preservation of large trees in the wild, a plantation of grafted trees, and introduction of seeds and/or seedlings to other parts of China and throughout the world, have been laid since M. glyptostroboides being discovered in 1940s. M. glyptostroboides is successfully recovered in number and distribution range now, but whether the genetic structure has been recovered and whether its introduced populations can regenerate naturally are unknown. In this dissertation, firstly I determined the phylogenetic position of M. glyptostroboides in Taxodiaceae species based on constructing phylogenetic tree. Secondly, I compared the genetic structure of artificial populations of M. glyptostroboides with the natural populations' and discuss the genetic consequence of the recovery. Thirdly, the natural regeneration ability of recovered populations was assessed from seed quality and seedling growth. At last, I discussed the factors that affected the genetic structure of recovery populations and provided some suggestions on the recovery of M. glyptostroboides.1. Using sequences of 4 chloroplast DNA (cpDNA) regions, including trnL IGS, trnL-trnF IGS and trnF gene, trnV gene and petG-trnP gene, as well as 3 mitochondrial DNA (mtDNA) regions, including atpA, Nad1, CoxIII gene, we explored the phylogenetic relationships of 15 species and 1 variety of 9 genera in Taxodiaceae. Five sections were classified in Taxodiaceae, i.e. section A (Glyptostrobus, Taxodium), section B (Cryptomeria), section C (Taiwania, Cunninghamia), section D (Metasequoia, Sequoiadendron, Sequoia) and section E (Athrotaxis). However, sections of A, B, C and D were more closely related than E indicated by mtDNA sequence, while cpDNA data indicated that A and B are closely related and C, D and E has a closely related relationship.(2) There were 88 mutation sites in 1168 sites of cpDNA combined sequence (7.53%), while...