Spatial Genetic Structure Of Abies Georgei, The Tree Line Species In Meili Snow Mountains

High altitude ecosystems are vulnerable to the effects of climate change-making tree line ecosystem increasingly attractive for ecological and conservation study. Moreover, there are few studies involving the analysis of spatial genetic structure (SGS), which is an essential understanding in population genetics as it provides information about ecological adaptation and evolution in plants and animals to aid conservation strategies. We studied population of Abies georgei Orr (Pinaceae), a relic species of the quaternary glacier period and a tree line species from Meili Snow Mountains. We genotyped657individuals of A. georgie across altitudinal range (high, H population,4150～4250m a.s.1; middle, M population,3800～3900m a.s.1); and, low, L population,3500～3600m a.s.l) through9pairs of fluorescent SSR markersusing R software, GeneAIEx6.5, STUCTURE2.3.4, and SPAGeDi1.3. In this study, we want to investigate the differences in genetic diversity and spatial genetic structure across altitudinal changes. We also want to understand the adaption and response to climate change in Meili Snow Mountains. Our results were as follows:(1) The genetic diversity of A. georgei is high with little difference in3populations, while the genetic variance among populations is low. The Nei’s index (He) and Shannon index (I) consistently increases with altitude, L population (He=8.11, I=2.071), M population (He=8.826,1=2.134), and, H population (He=0.848,1=2.235).(2) The spatial genetic structure (SGS) analysis of H population is stronger than M and L population, but the differences is not significant. The SGS analysis of equal distance groups (10m/group), indicates that the spatial autocorrelation is significantly positive in H population shorter than75m distance and greater in M and L populations, while the trend becomes random after75m. In population level, the SGS index Sp in H, M and L population is0.0138,0.003, and0.0023, respectively.(3) In Abies georgei, the heterozygosity is higher with the increase in tree age. According to the scatters of MLH and SMLH with tree DBH, as the tree becomes older, the loss of homozygosity is greater, the survival of heterozygous is increasingly high, which means the heterozygosity is higher.If genetic diversity is high but the variance is low, the gene flow is stronger, therefore, limiting dispersal processes. And the heterozygous may have adaptive advantage.