| Rhododendron aureum Georgi.(syn.Rh.Chrysanthum Pall.),a family of Ericaceae,is a perennial evergreen dwarf shrub and is the only bush in the Changbai Mountain area that can grow more than 1,000 meters above sea level in dark coniferous forest,birch forest,subalpine swamp and alpine tundra.In this study,the genetic diversity and genetic structure,reproduction mode,gene expression differences,interspecific relationships,community soil properties and microbial community structure were analyzed to elaborate the ecological adaptability of Rhododendron aureum.The main results are as follows:1.Using AFLP molecular markers,the genetic diversity and genetic structure of 36 wild R.aureum populations in Changbai Mountain area were analyzed by 10 pairs of selective primers.A total of 449 loci were detected,the percentage of polymorphic loci(PPL)is as high as 99.78%,the number of observed alleles(na)was 2.00,the number of effective alleles(ne)was 1.72,Nei's gene diversity(He)was 0.40,and Shannon's information index(I)was 0.58.The results showed that the R.aureum had high genetic diversity,whether grouped by geographical area or grouped by altitude(Table 2.6,2.7).The genetic diversity within population in dark coniferous forest(PPL = 2.45% in N7 and 18.71% in N8)and Wangtiane mountain(PPL = 25.61% in WTE1 and 26.59% in WTE2)was low,whereas genetic diversity within population in the remaining populations were higher(Table 2.5).53 outlier loci were found by using Baye Scan software on AFLP loci.The genetic distance of these loci was significantly correlated with geographical distance and environmental climatic factors.The outlier is the result of natural selection of R.aureum by environmental heterogeneity of the alpine.There was significant genetic differentiation(FST = 0.69)between the populations of R.aureum,and the gene flow was small(Nm = 0.39),and the overall clustering relationship among the populations was complicated.2.In order to further analyze the existing genetic relationship,here we selected cp DNA sequence which is relatively conservative than nucleus DNA to analyze the genetic diversity and genetic structure of R.aureum.The total length of the combined fragment of psb E-pet L and psb A-trn H was 1698 bp,and 16 haplotypes(H1-H16)were identified in 496 individuals.The nested clade phylogeographic analysis showed haplotypes H1 and H2 which were both contained in most populations are in the central position,indicating that the two haplotypes are primitive haplotypes.At the species level,haplotype diversity(Hd = 0.566)and nucleotide polymorphism(? = 0.47 × 10-3)also showed a high level of diversity.The genetic differentiation(FST = 0.18)was at a higher level,and the haplotype phylogeographic analysis showed that there was no obvious phylogeographic pattern.Neutral test was significant negative(Tajima's D =-1.825,P < 0.05,Fu & Li's D =-3.09637,P < 0.05,Fu & Li's F =-3.131,P < 0.02),and mismatch distribution showed clearly unimodal shape(Fig.2.16,2.17),indicating that the population of R.aureum experienced population expansion or bottleneck effect.3.In the field investigation,it was found that there were a large number of monoclonal populations of R.aureum in wild populations under natural conditions;and using AFLP molecular marker to study the clonal reproduction status of R.aureum,7-13 genets with an average of 9.8 genets was detected in the five big populations,indicating that the clonal reproduction is widespread.There was a significant difference in the clonal architecture of monoclonal population in the tundra and Betula ermanii forest(the length of spacer: 18.6±5.6 in tundra,29.7±9.7 in B.ermanii forest,P < 0.05;branch strength: 136.7±32.9 in tundra,43.4±12.3in B.ermanii forest,P < 0.05).The results showed that R.aureum had strong clonal plasticity and showed good adaptability to heterogeneous habitat.The clonal diversity of R.aureum is high(Simpson = 0.84,Fager's E = 0.85),indicating that there were both sexual reproduction and clonal propagation in the large population.4.Using the m RNA differential display technique and the real – time PCR,the leaves of R.aureum under different habitats were analyzed,and 17 different bands were obtained.After sequencing and BLAST,6 genes are highly homologous with the sequences as follows:(a)serine/threonine-protein phosphatase 4 regulatory subunit 2-A(PP4),which involved in the response of plants to drought and low temperature stress and with a high expression in populations X1706 and B2529;(b)photosystem I assembly protein ycf4(Ycf4),which involved in the light-dependent reaction in photosynthesis with high expression in populations B2529 and B2600;(c)phototropic-responsive NPH3 family protein(NPH3),which involved in the regulation of plant growth to light with a high expression in population B2300;(d)basic 7S globulin 2-like protein(B7SG),which involved in the growth and development regulation with high expression in population B2529 and B2600;(e)pentatricopeptide repeat-containing protein At5g40410,mitochondrial-like(PPR)which involved in the growth and development and adversity defense with high expression in population B2600;(f)receptor-like protein kinase(RLK)which involved in signal transduction in response to plant abiotic stress response and with high expression in populations X1706 and B2529.5.Eight R.aureum communities in different altitudes from 1800 m to 2600 m on the main peak of Changbai Mountain was investigated,83 species was found and which are belong to 58 genera and 31 families.There were differences in the biodiversity of R.aureum at different altitudes,among which the communities on typical tundra showed the most biodiversity(Plot 5-Plot 7: H = 0.42-0.423,D = 0.379-0.389,E = 0.264-0.267,R1 = 0.480,R2 = 0.260-0.270),indicating that the community structure is affected by the vertical landscape.The overall interspecific associations of R.aureum community was positively correlated(VR= 1.55,W=148.73,?2(0.95)64=82.529),indicating that the whole species can live together,promote each other,and jointly adapt to the mountain environment,the community structure is stable.R.aureum and its most associated vegetation were negatively correlated indicating that the competition relationship between R.aureum and its coexisting species is obvious.There is a positive correlation between the important value of R.aureum and the average temperature in the growing season,and the community biodiversity is negatively correlated with the average temperature in the growing season.6.By comparing the soil properties,enzyme activities,nitrogen cycling genes and soil microbial diversity and community structure of R.aureum community and non-R.aureum community,it was found that there was no significant difference in soil properties between the two types of communities,but the abundance of nutrient cycling genes and soil extracellular enzyme activity of R.aureum community was higher than that of non-R.aureum community,indicating that the nutrient cycling rate of R.aureum community was higher than that of non-R.aureum community.There was no significant difference in soil microbial ? diversity between the two types of communities,but the microbial community structure was significantly different.The results showed that the R.aureum community could affect the composition of soil microbes,accelerate the mineralization rate of nutrients and build a soil environment that was more suitable for their growth thus improving its ecological adaptability to the mountain environment. |
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