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资助项目
GST, P < 0.05) were exhibited by this species. The SAMOVA revealed seven diverging groups of related chlorotypes, six of them had distinct nonoverlapping geographical ranges: one in the northeast comprising 10 populations, a second with a southeast distribution comprising 22 populations, and the remaning four groups comprising 15 populations located in the west part of the species’ range along different river valleys. The genetic clustering of populations into three regions was also supported by analysis of molecular variance, which showed that most genetic variation (82.43%) was found among these three regions. Two clusters were distinguished by both phylogenetic analysis and genealogical analysis of chlorotypes, one consisting of chlorotypes from the western region and the second consisting of those from the eastern region. Significant genetic differences between the two regions might be attributed to vicariance and restricted gene flow, and this vicariance could be explained by the physical environmental heterogeneity on each side of the Tanaka-Kaiyong Line. Following the uplift of the Tibetan Plateau, the reorganization of the major river drainages was primarily caused by river separation and capture events. These historical events could change the distribution of S. davidii from fragmented to continuous (Upper/Lower Jinshajiang and Yalongjiang/Daduhe), and from continuous to fragmented (Nujiang and Jinshajiang/Honghe). However, spatial and temporal patterns of phylogeographic divergence are strongly associated with historical disjunction rather than modern drainage connections. Moreover, the following north-south split in the eastern region and effective isolation with their genetic diversity were essentially modelled by genetic drift. The higher chlorotype richness and genetic divergence for populations in western region compared with other two regions suggests that there were multipe refugia or in situ survival of S. davidii in the Himalayan-Hengduan Mountain region. Fixation of chlorotypes in the northeastern region and near fixation in the southeastern region suggest a recent colonization of these areas. We further found that this species underwent past range expansion around 37-303 thousand years ago (kya). The southeastern populations likely experienced a demographic expansion via unidirectional gene flow along rivers, while northeastern populations underwent a more northward expansion, both from initial populations (s) (21, 22, 23) preserved on eastern refugia (Jinshajiang). This process might have been accompanied with a series of founder effects or bottlenecks making populations genetically impoverished. 3. Phylogeographic analysisbased on nuclear sequence，We sequenced the nuclear (ncpGS) region in all populations sampled, recovering 23 nuclear haplotypes. Compared to cpDNA, both NST (0.470) and GST (0.338) were relatively lower, but NST was also significantly larger than GST. 37.10% of the total variation was distributed among regions which was much lower than that shown by chlorotypes. Thus, more extensive distribution of nuclear haplotypes was exhibited across the geographical range instead of the strong population subdivision observed in chlorotypes. Similarly to the chloroplast data, we found that genetic differentiation of nDNA was positively correlated with the geographical distance, but the increase in the geographical distance between populations did not increase the genetic differentiation of nDNA as rapidly as that of cpDNA. These contrasting levels between the chloroplast and nuclear genomes of S. davidii are likely due to limited gene flow of cpDNA by seeds vs. the extensive gene flow of nDNA by wind-mediated pollen in the population history. We also determined from nuclear markers that haplotype diversity was reduced in the southeastern and northeastern regions due to the loss of rare haplotypes in western region. This reduction of gene diversity is also a signature of founder events or recent bottleneck during post-glacial colonization. However, nuclear diversity within populations remains high. This provides evidence that regionally pollen flow might be sufficiently high to blur the genetic identity of founder populations over a reasonably large spatial scale.3. Relationships among three varieties，The phylogenetic analysis identified two phylogroups of chlorotypes, corresponding to S. davidii var. davidii and var. chuansinesis. The former was distinguished by the abscence of predonminant nuclear haplotype H1 of the latter. The monophyletic group of chlorotypes in var. davidii and var. liangshanesis showed their relatively close relationship. And their genetic divergence from the third variety appears to be relative to their slight morphological difference in leaf size and the divergent environmental niche spaces they occupy. Thus, the observed differences in morphological characters between var. chuansinesis and other two varieties can be explained by the seed dispersal limitation illustrated above (as inferred by geographical separation) and by environmental heterogeneity (as inferred by precipitation or elevation) or by a combination of both. After all, the geological changes, drainage reorganization, and floristic differences following the Himalayan uplift have been suggested to affect the genetic structure of S. davidii. These results provide new insights into the phylogeographic pattern of plants in China. In addition, the unique population genetic structure found in S. davidii has provided important insights into the evolutionary history of this species. The genetic profile uncovered in this study is also critical for its conservation management. Our study has uncovered the existence of at least two ‘evolutionary significant units’ independent units within S. davidii, corresponding to var. davidii from eastern region and var. chuansinensis from western region. The conservation efforts should first focus on most western populations and on the southeastern ones exhibiting high levels of genetic diversity, while the genetically homogeneous northeastern populations located in the degraded Loess Plateau should require much greater conservation 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investigating sympatric distribution of Rhododendron irroratum, examing the variation of floral characters and sequencing the ITS and other chloroplast segements, we find that (1) R. irroratum might be of hybrid origin, with its maternal parent R. delavayi or R. decorum. (2) The ancestral haplotype of R. irroratum might be identical to that of R. decorum, and it is under ongoing introgression from R. delavayi. 1. The natural distribution, Seven distribution sites of R. irroratum in Guizhou and Yunnan province were investigated. The result shows that R. irroratum is sympatric with R. delavayi, R. decorum and R. agastum. R. delavayi is widespread across the above-mentioned seven sites, whereas R. agastum is scarce in DaPingDi, HuaDianBa and HeQing sites. R. irroratum and R. agastum distribute at the higher elevation compared to that of R. decorum, while R. delavayi is of widespread distribution across both regions of R. decorum and R. irroratum.2. Floral variation of R. irroratum among populations, The floral characters remain vary within and among populations except for the stamen number and the petal number. Seven floral characters correlates with each other among populations, of 28 different combinations, 26 reveal significant correlation, and 23 extremely significant correlation. The PCA analysis shows that the first two components account for 52.18% of the total variation. The dendrogram tree is divided into four main parts, roughly representing the respective populations, which is constructed using 22 R. irroratum individuals. 3. Putative Development and the transferability test of SSR makers, Fifteen microsatellite loci were developed and characterized in R. delavayi. The average allele number of these microsatellites was 4 per locus, ranging from 3 to 6. The ranges of expected (HE) and observed (HO) heterozygosities were 0.0365-0.7091 and 0.0263-0.9512, respectively. Seven loci (R-111, R-112, R-147, R-299, R-320, R-335, and R-544) deviated significantly from the HWE (P﹤0.01). No significant linkage disequilibrium was detected between locus pairs except for three locus pairs: R-299 and R-544, R-166 and R-320, R-111 and R-320. Cross-species amplification in R. agastum, R. decorum, and R. irroratum showed that a subset of these markers holds promise for congeneric species study.4. ITS, matK, trnH-psbA and rbcL sequences. R. delavayi has six sites different from that of R. decorum in its ITS region, whereas R. agastum reveals double peaks at the corresponding sites and R. irroratum is identical to that of R. delavayi. The chloroplast segements show that some R. irroratum individuals share the same haplotype with R. delavayi and others share them with R. decorum.","jscount":"1","jsurl":"/simple-search?field1=all&field=location.comm.id&advanced=false&query1=Polyploidy&&fq=dc.project.title_filter%3AThrough%5C+investigating%5C+sympatric%5C+distribution%5C+of%5C+Rhododendron%5C+irroratum%2C%5C+examing%5C+the%5C+variation%5C+of%5C+floral%5C+characters%5C+and%5C+sequencing%5C+the%5C+ITS%5C+and%5C+other%5C+chloroplast%5C+segements%2C%5C+we%5C+find%5C+that%5C+%5C%281%5C%29%5C+R.%5C+irroratum%5C+might%5C+be%5C+of%5C+hybrid%5C+origin%2C%5C+with%5C+its%5C+maternal%5C+parent%5C+R.%5C+delavayi%5C+or%5C+R.%5C+decorum.%5C+%5C%282%5C%29%5C+The%5C+ancestral%5C+haplotype%5C+of%5C+R.%5C+irroratum%5C+might%5C+be%5C+identical%5C+to%5C+that%5C+of%5C+R.%5C+decorum%2C%5C+and%5C+it%5C+is%5C+under%5C+ongoing%5C+introgression%5C+from%5C+R.%5C+delavayi.%5C+1.%5C+The%5C+natural%5C+distribution%2C%5C+Seven%5C+distribution%5C+sites%5C+of%5C+R.%5C+irroratum%5C+in%5C+Guizhou%5C+and%5C+Yunnan%5C+province%5C+were%5C+investigated.%5C+The%5C+result%5C+shows%5C+that%5C+R.%5C+irroratum%5C+is%5C+sympatric%5C+with%5C+R.%5C+delavayi%2C%5C+R.%5C+decorum%5C+and%5C+R.%5C+agastum.%5C+R.%5C+delavayi%5C+is%5C+widespread%5C+across%5C+the%5C+above%5C-mentioned%5C+seven%5C+sites%2C%5C+whereas%5C+R.%5C+agastum%5C+is%5C+scarce%5C+in%5C+DaPingDi%2C%5C+HuaDianBa%5C+and%5C+HeQing%5C+sites.%5C+R.%5C+irroratum%5C+and%5C+R.%5C+agastum%5C+distribute%5C+at%5C+the%5C+higher%5C+elevation%5C+compared%5C+to%5C+that%5C+of%5C+R.%5C+decorum%2C%5C+while%5C+R.%5C+delavayi%5C+is%5C+of%5C+widespread%5C+distribution%5C+across%5C+both%5C+regions%5C+of%5C+R.%5C+decorum%5C+and%5C+R.%5C+irroratum.2.%5C+Floral%5C+variation%5C+of%5C+R.%5C+irroratum%5C+among%5C+populations%2C%5C+The%5C+floral%5C+characters%5C+remain%5C+vary%5C+within%5C+and%5C+among%5C+populations%5C+except%5C+for%5C+the%5C+stamen%5C+number%5C+and%5C+the%5C+petal%5C+number.%5C+Seven%5C+floral%5C+characters%5C+correlates%5C+with%5C+each%5C+other%5C+among%5C+populations%2C%5C+of%5C+28%5C+different%5C+combinations%2C%5C+26%5C+reveal%5C+significant%5C+correlation%2C%5C+and%5C+23%5C+extremely%5C+significant%5C+correlation.%5C+The%5C+PCA%5C+analysis%5C+shows%5C+that%5C+the%5C+first%5C+two%5C+components%5C+account%5C+for%5C+52.18%25%5C+of%5C+the%5C+total%5C+variation.%5C+The%5C+dendrogram%5C+tree%5C+is%5C+divided%5C+into%5C+four%5C+main%5C+parts%2C%5C+roughly%5C+representing%5C+the%5C+respective%5C+populations%2C%5C+which%5C+is%5C+constructed%5C+using%5C+22%5C+R.%5C+irroratum%5C+individuals.%5C+3.%5C+Putative%5C+Development%5C+and%5C+the%5C+transferability%5C+test%5C+of%5C+SSR%5C+makers%2C%5C+Fifteen%5C+microsatellite%5C+loci%5C+were%5C+developed%5C+and%5C+characterized%5C+in%5C+R.%5C+delavayi.%5C+The%5C+average%5C+allele%5C+number%5C+of%5C+these%5C+microsatellites%5C+was%5C+4%5C+per%5C+locus%2C%5C+ranging%5C+from%5C+3%5C+to%5C+6.%5C+The%5C+ranges%5C+of%5C+expected%5C+%5C%28HE%5C%29%5C+and%5C+observed%5C+%5C%28HO%5C%29%5C+heterozygosities%5C+were%5C+0.0365%5C-0.7091%5C+and%5C+0.0263%5C-0.9512%2C%5C+respectively.%5C+Seven%5C+loci%5C+%5C%28R%5C-111%2C%5C+R%5C-112%2C%5C+R%5C-147%2C%5C+R%5C-299%2C%5C+R%5C-320%2C%5C+R%5C-335%2C%5C+and%5C+R%5C-544%5C%29%5C+deviated%5C+significantly%5C+from%5C+the%5C+HWE%5C+%5C%28P%EF%B9%A40.01%5C%29.%5C+No%5C+significant%5C+linkage%5C+disequilibrium%5C+was%5C+detected%5C+between%5C+locus%5C+pairs%5C+except%5C+for%5C+three%5C+locus%5C+pairs%5C%3A%5C+R%5C-299%5C+and%5C+R%5C-544%2C%5C+R%5C-166%5C+and%5C+R%5C-320%2C%5C+R%5C-111%5C+and%5C+R%5C-320.%5C+Cross%5C-species%5C+amplification%5C+in%5C+R.%5C+agastum%2C%5C+R.%5C+decorum%2C%5C+and%5C+R.%5C+irroratum%5C+showed%5C+that%5C+a%5C+subset%5C+of%5C+these%5C+markers%5C+holds%5C+promise%5C+for%5C+congeneric%5C+species%5C+study.4.%5C+ITS%2C%5C+matK%2C%5C+trnH%5C-psbA%5C+and%5C+rbcL%5C+sequences.%5C+R.%5C+delavayi%5C+has%5C+six%5C+sites%5C+different%5C+from%5C+that%5C+of%5C+R.%5C+decorum%5C+in%5C+its%5C+ITS%5C+region%2C%5C+whereas%5C+R.%5C+agastum%5C+reveals%5C+double%5C+peaks%5C+at%5C+the%5C+corresponding%5C+sites%5C+and%5C+R.%5C+irroratum%5C+is%5C+identical%5C+to%5C+that%5C+of%5C+R.%5C+delavayi.%5C+The%5C+chloroplast%5C+segements%5C+show%5C+that%5C+some%5C+R.%5C+irroratum%5C+individuals%5C+share%5C+the%5C+same%5C+haplotype%5C+with%5C+R.%5C+delavayi%5C+and%5C+others%5C+share%5C+them%5C+with%5C+R.%5C+decorum."},{"jsname":"lastIndexed","jscount":"2024-04-25"}],"资助项目","dc.project.title_filter")'>
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