| Since the first report on Ophiocordyceps sinensis by Berkeley in 1843, many researchers have investigated carefully on its morphology, genetics, chemistry and ecology. In spite of this, study on the morphological characters, genetic structure and ecological distribution of O. sinensis with population as unit has rarely been reported. Through phylogeography method and suitable area simulation, morphological variation pattern, genetic differentiation, suitable distribution pattern and its response to the global warming of O. sinensis with population as unit were researched in this study.The Hengduan Mountains was the genetic diversity center, genetic differentiation center for O. sinensis, and is probably the origin center for this species. In this study,53 populations and total 503 Internal transcribed spacer (ITS) sequences were used.43 haplotypes were obtained. The haplotype proportion and nucleotide diversity of the Hengduan Mountains were 55.8% and 6.47, respectively. Both of them were higher than those of Tibet (44.19%,4.67) and eastern Qinghai-Tibet Plateau (QTP) (41.82%, 2.32). The haplotypes of Hengduan Mountains but also contained the primary haplotypes of Tibet and eastern QTP. Phylogenetic analysis indicated that the first differentation of ITS haplotype occurred at the Hengduan Mountains. Furthermore, distribution center and genetic diversity center of its host was also suggested being the Hengduan Mountains. Through investigation for eight years, many relative species of O. sinensis were found locating at the Hengduan Mountains, especially the known oldest species of genus Ophiocordyceps, O. bispora, was also at the Hengduan Mountains.Since the origin at Hengduan Mountains, O. sinensis populations dispersed to the eastern QTP and Tibet successively. As the indicator species of QTP, the evolution of O. sinensis was tightly linked to the uplifting of QTP. The sequence of being land for QTP set a tone for the dispersion route of O. sinensis. Genetic differentiation coefficient (Fs1) indicated that the populations in Tibet and Hengduan Mountains were closer, meaning that the populations in eastern QTP had been differentiated for longer time. The dispersion route was speculated as follows. Firstly, the ancestral haplotype H15 originated in the Hengduan Mountains and differentiated into derived populations presented by haplotype H33 in situ; secondly, some populations dispersed to the eastern QTP and finally differentiated into group eQTP; and thirdly, part of populations from Hengduan Mountains migrated toward the Tibet.Geological events in QTP caused and aggravated the genetic differentiations of O. sinensis populations. Phylogenetic tree of ITS haplotypes indicated that each differentiation after 4.54 Mya was coupling to the Qingzang Movement A (3.6-3.4 Mya), Qingzang Movement B (2.6-2.5 Mya), rapid uplifting (2.5-1.8 Mya) and Kunhuang Movement (1.2-0.6 Mya). Long time planation of plateau ended at about 4.54 Mya and soon afterwards the QTP began to uplift rapidly again, which caused the relevant genetic differentiation and adaptation O. sinensis populations. As the endemic species to QTP, geological events in QTP caused the genetic differentiations of O. sinensis populations. At present, the uplifting of QTP is continuing and accelerating (Gonghe Movement,0.6 Mya to present), which would further aggravate the genetic differentiations of O. sinensis populations.Topography of the Hengduan Mountains generated serious geographical isolation for O. sinensis populations and caused severe genetic differentiation of O. sinensis populations in this region. Based on EF1-α intron, EF1-α extron, rpb1,β-tubulin, MAT1-2-1 and cytb sequences, the genetic isolation analysis of 20 populations indicated that there were severe genetic isolation among populations in Hengduan Mountains, especially in the northwestern Yunnan. There are seven mountains in Hengduan Mountains extend from north to south. They are Qionglai Mountains, the Big Mountains, Shaluli Mountains, Mangkang Mountain, Nu Mountain, Gaoligong Mountain and Boxoila Ling. There are also five great rivers among them and they are Dadu River, Ya-lung River, the Jinsha River, Lantsang and Nujiang River. Mountains and rivers become natural barriers of dispersion for many species. Geological isolation was one of the main reasons for genetic isolation. In Hengduan Mountains, the isolation from barranca was greater than isolation from high mountains.370 sample sites were collected. Through statistic analysis and model simulation of MaxEnt indicated that total suitable area of O. sinensis was 945620.8 KM2, covering Tibet, Qinghai, Gansu, Sichuan and Yunnan in China and also covering Bhutan, Nepal and Uttarakhand of India. The westernmost range was at east longitude 73°41’; the northernmost range was at northern latitude 38°06’; the easternmost range was at east longitude 103°55’and the southernmost range was at northern latitude 27°01’. Normal suitable area was largest and was up to 439163.19 KM2, while low suitable area was up to 395502.35 KM2, and the high suitable area was 110955.26 KM2. Among 19 ecological factors, max temperature of warmest month was the greatest and the limited factor for the growth and distribution of O. sinensis. Suitable level of Uttarakhand of India, southern Nagqu in Tibet, northern Linzhi area, Qinghai Lake area in Qinghai, western Sichuan and northwestern Yunnan were relatively higher.In the face of global warming, the distribution pattern of O. sinensis would change little and total distribution area would increase a little but insignificantly. Changes in suitable areas at different elevations were also predicted. Expansion of both the lower (2500-2800 m) and upper altitudinal limits (4600-5500 m) were observed in all of the future climate change pathways, while shrinking mainly occurred in the altitude range of approximately 4200-4700 m. In the face of global warming, O. sinensis would migrate to higher altitude to keep its present ecological niche, or migrate to lower altitude to adapt new ecological niche.19 populations of O. sinensis were analyzed on 22 characters of sclerotium, stroma and reproduction part. There was significantly correlation between the characters of sclerotium and stroma. So it was suggested that length of sclerotium and diameter of lower stroma should be taken as the qualification standard of morphology. In species level, average value of length of sclerotium was 3.646 cm, while that of diameter of lower stroma was 0.275 cm. Percent of populations variance of sclerotium characters was 49.77%, while percent of individual variance was 50.23%. Percent of populations variance of stroma characters was 66.84%. while percent of individual variance was 33.16%, which indicated that the variance of stroma characters were mainly from the populations. Percent of populations variance of eight characters of reproduction part was 37.69%, while percent of individual variance was 62.31%, which indicated that the variance of reproduction part characters were mainly from the individuals within populations.In conclusion, the Hengduan Mountains might be the genetic diversity center, genetic differentiation center for O. sinensis, and might be probably the origin center for this species. Since the origin at Hengduan Mountains, O. sinensis populations dispersed to the eastern QTP and Tibet successively. Geological events in QTP caused and aggravated the genetic differentiations of O. sinensis populations. Especially the topography of the Hengduan Mountains generated serious geographical isolation for O. sinensis populations and caused severe genetic differentiation of O. sinensis populations in this region. Uttarakhand of India, southern Nagqu in Tibet, northern Linzhi area, Qinghai Lake area in Qinghai, western Sichuan and northwestern Yunnan had both high suitable level and genetic diversity, so these areas were suggested being conservation areas in situ. In the face of global warming,O. sinensis would migrate to higher altitude to keep its present ecological niche, or migrate to lower altitude to adapt new ecological niche. Expect building conservation areas in situ, artificial culture of O. sinensis would be helpful to the protection and sustainable utilization of this species. |
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