The DNA Composite Bar Code Technology Was Used To Study The Aquatic Animal Diversity On The Northern Slope Of Qinling Mountain

The accurate identification of species is foundmental for understanding nature and conducting biological research. Traditional morphological-based species identification methods that through observing the morphology of organism to identify species, and are heavenly dependent the experienced taxonomists. Many species have been identified by this method, and have greatly enriched the global biodiversity. But this conventional method has some shortcomings, such as profound professional requirements, spending too much time, and difficult to correctly identify the cryptic species and the species that possesses phenotypic plasticity and genetic variability.With the development of molecular biology technology, especially, the DNA sequencing and PCR amplification, two new identification methods, DNA barcoding and DNA metabarcoding, were devised to offset the deficiency of morphological-based species identification in some extent. Using the short DNA sequences that have enough variation to speed and accurate species identification is the key stone for those two methods. DNA barcoding can identify the sample which contains one single organism, for the sample that contains many organisms, it may feeble to rapid and accurate species identification. DNA metabarcoding, a technique based on next-generation genetic sequencing, enables the rapid characterization of species composition in bulk biodiversity samples or when analyzing environmental DNA, and thus facilitates comprehensive, large-scale biodiversity assessments and monitoring.The north slope of Qinling Mountains is the important segment in Qinling Mountains, it includes a series of valleys traversed by mountain streams of various sizes. Although these streams potentially contain an array of aquatic organisms, the complexity of the environment and the presence of small, cryptic, rare, or poorly characterized species makes studying the aquatic biodiversity of these streams a challenge. The goal of this study was to use DNA metabarcoding to examine the composition of both the aquatic fauna and the aquatic communities as a whole in the north slope of Qinling Mountain streams, employing alpha diversity, community composition analyses and cluster analyses to evaluate differences in biodiversity from samples collected from different locations. For this purpose,10 samples containing both zooplankton and zoobenthos were collected from downstream and upstream locations of five streams (Jin Longxia, Shi Bianyu, Feng Yukou, Mt.Nanwutai and Meridian Valley) in the north slope of Qinling Mountains, between August and September 2014. The mainresults obtained from this study are as follows:(1) The amplicons of 18S ribosomal RNA (18S rRNA) gene were sequenced on an Illumina MiSeq platform, results in 1,969,984 raw sequences, after quality filtering, paired-end assembly and chimera filtering, we obtained 84,4510 high quality sequences, and got 2,423 OTUs via OTU cluster and annotation. In the same way, for cytochrome c oxidase subunit I (CO I) gene, we acquired 1,037,905 raw sequences,304,030 high quality sequences and 2,738 OTUs.(2) Analysis of the fauna composition revealed that a total of 86 orders, from 46 classes, and 10 phyla were identifiable in the total group of samples using the two gene markers. Individually,52 orders, from 42 classes, and 9 phyla were identified using the 18S rRNA sequences, and 36 orders, from 11 classes, and 5 phyla were identified using the CO I sequences, demonstrating that the two gene markers together resulted in a higher rate of identification than either marker alone.(3) With regard to community composition, analysis of CO I gene sequences revealed that the Coleoptera, Diptera, Stylommatophora, Lepidoptera and Megaloptera were the most common taxa, with lower occurrences of Protozoa and Rotifera. Analysis of community composition using the 18S rRNA gene sequences, on the other hand, indicated three main groups in the samples, namely the Arthropda, Mollusca and Platyhelminthes. However, when we combined the two gene makers, the Turbellaria, Gastropoda and Inseta showed high percentage.(4) Both the fauna composition and community composition analyses showed that either the number of groups, or the complexity of community structure and the nummber of dominant species in the downstream samples was higher than that in the upstream samples.(5) Alpha diversity analysis revealed that the sampling plot of Feng Yukou that most intensively affected by human activities had relatively low species richness and diversity compared with the sampling plots (Mt.Nanwutai, Shi Bianyu and Meridian Valley) that nature or mild affected by human activities, suggesting that aquatic biodiversity may be improved if a location has a certain degree of external interference, but when the external interference too strong, biodiversity will decline.(6) Cluster analysis showed that the downstream and upstream sample of Shi Bianyu, the downstream sample of Jin Longxia and Mt.Nanwutai have similar community structure, but the upstream sample of Mt.Nanwutai have obvious community variations with other samples. Those all demonstrated that community variations may be very obvious when samples collected from different environments, on the contrary, when samples collected from similar environments, the community similarity values may be relatively high.