| Guizhou karst plateau wetland is known as a"biological gene bank"with its complex ecosystem and rich biodiversity.The total area is up to 16447 km~2,accounting for 9.34%of the land area of the whole province and 2.8%of the national wetland area.However,fungi are often ignored as an important decomposer in wetland ecosystem.The aquatic fungi in the wetland of Guizhou karst plateau are mainly obligate or opportunistic fungi from freshwater habitats.Freshwater fungi represent a high diversity and has been reported from Ascomycota,Basidiomycota,Blastocladiomycota,Chytridiomycota,Cryptomycota,Oomycota and Zygomycota.The population composition and diversity of freshwater fungi have important theoretical significance and practical value in the earth's ecological cycle,development of industrial and agricultural microorganisms and environmental governance and monitoring.Therefore,it is necessary to carry out the investigation of freshwater fungi of karst wetland from Guizhou Province,including fungal collection,classification and preservation,and the analyses of fungal community and diversity.In this study,samples of submerged decaying wood and branches,aquatic grasses were collected from five typical wetlands from four directions of Guizhou Province.Single spore isolation,morphological examination and phylogenetic analysis were carried out following the scientific methods.The community composition and diversity of freshwater fungi from lenti and lotic water and from different elevations(low,medium and high elevations)were analyzed.The high-throughput sequencing was firstly used to study the freshwater fungi from the wetland of Caohai National Nature Reserve.Three environmental factors were selected to analyze the correlation between freshwater fungal diversity and environmental factors.The results are as follows:1.In total,580 specimens were collected,of which 396 were valid specimens.Finally,162strains were isolated and purified.Sequences of 4-5 genes or DNA fragments(BT,ITS,LSU,RPB2,SSU,TEF1?and TUB)were amplified for each strain,and 462 sequences were obtained and uploaded to Gen Bank.Based on the morphological characters and multi-gene phylogenetic analysis,162 strains were classified into Ascomycetes,belonging to five classes Dothideomycetes,Sordariomycetes,Eurotiomycetes,Leotiomycetes and Orbiliomycetes,containing 22 orders,46families,68 genera and 102 species with one new family,4 new genera,39 new species,2 new combinations,11 new records in China,3 morphological subspecies,1 sexual morph.Total 204herbarium specimens and 816 pure living cultures(each species with 2 herbarium specimens and 8tube cultures)were deposited in Guizhou Academy of Agriculture Sciences and Guizhou Microbiological Culture Collection Center?2.Of the 162 strains,91 strains and 71 strains were isolated from lentic and lotic water,respectively.Analysis of the freshwater fungal community composition and diversity revealed that the Shannon-Wiener index(H?)and Simpson index(D)of lotic water were higher than that of lentic water.Based on the Berger-Parker dominance index,the highest relative abundant species in both lentic water(dominance index 0.389)and lotic water(dominance index 0.259)was Pleosporales species.It indicated that the diversity of freshwater fungi is closely related to the fluidity of water body.From the order,family and general level,the similarity indices of lotic and lentic water were 0.667,0.375 and 0.225,indicating that the species composition of freshwater fungi from lentic water and lotic water are significantly different.29 strains were isolated from low altitude,75 strains from middle altitude and 58 strains from high altitude.The Shannon-Wiener index(H?)and the Simpson index(D)in the middle altitude area reached the highest point:2.585 and 0.907,followed by 2.205 and 0.886 of the low altitude.The lowest diversity index was 1.956 and 0.818 at the high altitude in Caohai region.It showed that the middle altitude region has the highest diversity,the low altitude region with second highest diversity and the high-altitude region with the lowest diversity.Based on the Berger-Parker dominance index(dominance indices 0.308,0.264 and 0.400 at the low,middle and high-altitude region),the highest relative abundance species from three altitudes are Pleosporales species.It indicated that the diversity of freshwater fungi is closely related to altitude with the diversity reduced from middle altitude to both ends.Thus,the suitable growing environment of freshwater ascomycetes is the warm environment at middle altitude.3.The diversity and composition of freshwater fungi in four seasons of surface water were systematically analyzed by high-throughput sequencing in Guizhou Karst Plateau Wetland Caohai National Nature Reserve.The results showed that freshwater ascomycetes(35.22%)were the most common species in Caohai,the second is basidiomycetes(17.99%).Autumn had the highest species richness,the ACE index and Chao1 index are 973.404±298.857 and 957.459±276.091respectively and spring has the lowest species richness,the ACE index and Chao1 index are489.744±56.552 and 483.925±56.551 respectively.In summer,freshwater fungi had the highest diversity,Shannon index and Simpson index were 4.197±0.559 and 0.95±0.026 respectively;in spring,the diversity was the lowest,Shannon index and Simpson index were 3.682±0.319 and0.917±0.03 respectively.There was no significant difference in the diversity of freshwater fungi between annual seasons.Based on the effects of water temperature,p H and dissolved oxygen in the freshwater fungal community composition,it could be concluded that water temperature is the most important environmental factor affecting for the freshwater fungal community composition,but the effects are different with seasons and are more significant in spring and summer,followed by dissolved oxygen,while dissolved oxygen does not show obvious seasonality.The p H showed higher effect in winter and autumn. |
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