Metasequoia Glyptostroboides: Introduction Of Artificial Populations And Viability Analysis Of Natural Populations

Metasequoia glyptostroboides Hu et Cheng (Taxodiaceae), a well-known "living fossil" plant, is endemic to China. Since it was first discovered in 1940s, conservation strategies were developed. So far, it has been introduced to 26 provinces in China and more than 50 countries throughout the world. However, the introduction quality and genetic information were important to the new populations. In addition, the natural habitats were destructed seriously due to human excessive disturbances, resulting in a severely regeneration limitation.In our study, polymorphic microsatellite loci were successfully isolated from M. glyptostroboides and applied them to examine population genetic structure of artificial and wild populations. The main results are as follows:1. A total of 11 microsatellite markers were developed in M. glyptostroboides using a magnetosphere enrichment protocol.2. Eight of those polymorphic markers were used to compare the difference genetic information between artificial populations and natural populations. Our results showed that the GST of artificial populations (0.074) was lower than that of natural populations (0.117), and Fjs was much higher (0.195 and 0.090, respectively), indicating much more similar genetic composition among artificial populations due to the single tree source. The average alleles and allele richness of artificial populations were a little higher than those of the wild populations, suggesting an extensive source of artificial populations. Genetic contributions analysis of each wild populations showed YZ and GQ were the most important ones on maintaining genetic diversity and genetic distinctiveness of M. glyptostroboides, which suggested the two populations were the conservation priorities. The natural populations could be defined into 2 clusters by STRUCTURE.3. UPGMA showed most artificial populations (expect TS and BZ) were in the same group with 3 natural populations of YZ, XB and GQ, which suggested they were introduced mainly from these 3 populations. Assignment test and parentage analysis showed that artificial populations introduced mainly from 3 populations YZ, XB and MD, but there were no difference in different introduced years. Our results revealed that YZ and XB were the primary sources. Based on the two populations were in the same cluster with the STRUCTURE analysis, we suggested that wild populations of another cluster (such as XG and DB) should be selected as introduction sources of M. glyptostroboides.4. Population viability analysis on natural populations showed population size growing under the near-natural transition pattern (λ=1.6570) while declining mainly due to poor regeneration in current state (2=0.9967). The population will reach a quasi-extinction threshold of population size of 50 and 500 in the coming 1600 and 600 years, respectively. The ratio of productive adults transiting into seedlings (a 13) is the most important factor in the life history. Our results suggested that there would be 25,000 seedlings each year, the population size may be successfully maintained.We suggested that reduction of human interfere to improve the natural regeneration of M. glyptostroboides. In addition, introduction should carry out considering genetic diversity simultaneously.