| Gymnocarpos przewalskii is a semi-shrub of coriolaceae protected at the national level.It is an important plant resource for the ancient Mediterranean relict plants which is of great significance to the formation of desertification in western China and Central Asia and desert vegetation.The distribution of Gymnocarpos przewalskii was patchy,the number of population obviously decreased and the endangered grade became more and more serious because of the climate change,the fragile distribution system,the more extreme climate and the distribution of human factors.Therefore,it is very important to explore the distribution characteristics of population under climate change and adaptability of trait variation.This paper discussed the adaptability of the population of Gymnocarpos przewalskii and the variation of traits in different habitats based on the theory of niche model,anatomy,ecological chemical metrology and molecular genetics.The results are showed as follows:1.The MAXENT model was used to predict the dominant factor of the change and influence of the population of Gymnocarpos przewalskii population based on the information of climate and distribution.The results showed that the distribution area of Gymnocarpos przewalskii was largest in the last glacial period and the habitat area is gradually reduced with the climate change in the ice age.However,some of the shelter area was made by the blocking of the Qilian Mountains,the Altun mountains,the Kunlun Mountains and the Helan Mountains in the ice age,the shelter is mainly located in Gansu Hexi Corridor(Shule River,the river basin),Yumuan off the northwest(hai Inner Mongolia(Yabuli)and Xinjiang(Tarim)and other basins.After the glacial period,the distribution area of the Gymnocarpos przewalskii increased with the increase of temperature.At present,it is mainly distributed in most of the Hexi Corridor of Gansu,some parts of Xinjiang and the central and western regions of Inner Mongolia and Ningxia.The suitable habitat gradually contraction to the Gansu Hexi corridor area narrowed in the future climate scenario.Knife cutting method showed that annual rainfall and temperature of coldest season are the determinants for the distribution of Gymnocarpos przewalskii.2.The main climatic factors affecting distribution of Gymnocarpos przewalskii are annual precipitation,annual mean temperature and annual sunshine hours based on the analysis of climatic,soil physical and chemical properties,vegetation characteristics of 12 geographical populations.The soil types are gray desert soil,gray brown desert soil and brown desert soil with low nutrient content and high content of chloride ion,sulfate ion and calcium ion which is neutral or weakly alkaline.Medieval Mediterranean,West Asia to Central Asia has the most of distribution of flora fauna(48%),followed by the North temperate distribution(24%)and the world distribution(12.8%)and temperate genus has an absolute advantage.Clustering analysis and climatic characteristics,soil factor characteristics and community species composition reflect that precipitation is the key reason resulting in the distribution of environmental heterogeneity in distribution area of Gymnocarpos przewalskii.3.The morphological structure of Gymnocarpos przewalskii has rich drought adaptability,such as plant miniaturization,stomatal subsidence,the number of changes in stomatal size and number,special structure of leaf tissue.The structure of Gymnocarpos przewalskii was obviously fleshy,ring-type mesophyll fence structure and significant dif-ference between structure of the far axis and the near axis.The mesophyll was storage organization,the cell morphology was irregular and the volume was larger.Veins was parallelled vein and two annular distribution of the lateral veins developed with storage tissue inside and fence organization outside.There are differences in the degree of organization development of the frontal and near-axis fences.The surrounded irregular cells of fence organization is different,larger in volume and loose water storage tissues arranged.The coefficient of variation of the 22 characteristics of phenotypic,leaf epidermis and structure of Gymnocarpos przewalskii was 0.116-0.185,the plasticity index was 0.298?0.397,and the variability and plasticity of the Gymnocarpos przewalskii were large which distributed in Subei County and Aixi County,Gansu Province,indicating the high population adaptability.The analysis of plant morphology,leaf epidermal characteristics and leaf structure based on principal component analysis and factor clustering showed that plant height,crown width,size and number,microtubule tissue and leaf thickness of Gymnocarpos przewalski changed in climate soil environment caused by precipitation.4.The results of chemometrics analysis showed that the variation of leaf C content was 319.15?493.98 mg·g-1 the variation of leaf N content was 5.41?28.03 mg·g-1 and the variation of leaf P content was 0.56?1.36 mg·g-1.There were significant difference of chemometrics characteristics between populations,the average values were lower than that of global terrestrial plants(1251 species)and Chinese plants(554 species).Precipitation resulted in high nitrogen and low phosphorus adaptation characteristics of Gymnocarpos przewalskii.The N:P of leaves of Gymnocarpos przewalskii was 26.09,indicating that the leaf was limited by phosphorus while P content was susceptible to temperature.20?40cm was the main absorption soil layer for leaf C,N and P of Gymnocarpos przewalskii.The variation of ecological and chemical characteristics of different populations was(8.930?15.703),and the variation of Gymnocarpos przewalskii population in Liuyuan Town and Subei County of Gansu Province was higher.5.The results of genetic diversity analysis showed that the percentage of polymorphic loci(PPB)was 90.01%and Nei's diversity index(He)was 0.2488 by using ISSR markers.The variation of PPB was 61.54%?81.12%at the population level with an average value of 67.37%which showed high genetic diversity.Nei's gene differentiation coefficient(Gst)was 0.2790,indicating small genetic differentiation among populations and abundant genetic variation.The results of UPGMA and PCA showed that 12 populations could be divided into four groups according to their genetic distance and there was correlation between genetic distance and geographical distance while there were correlations between environmental factors such as altitude,temperature,soil nitrogen content and total salt content factors and population genetic diversity. |
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