The Study On The Classification And Molecular Systematics Of Neidium In China

The genus Neidium Pfitzer belongs to Bacillariophyta,Bacillariophyceae,Naviculales,Neidiaceae.It is a unique and distinct characteristic group which plays an important role in the evolution of freshwater diatom.This genus is a very common genus with more than 500 taxa in the world.However,it continues to be confusion over some species and synonyms makes the classification of this genus difficult.We have summarized the genus Neidium which has been reported in China.Through many field investigations,the collected Neidium species were examined using LM and SEM images.As well,we can explore the taxonomic characters by the kinds of morphological structures to make clear the species diversity and the flora of this genus.In addition,isolated Neidium individuals are sequenced for rbc L,psbC and 18 S r DNA genes.The sequence data is concatenated to construct phylogenetic trees using Neighbor joining?Maximum Likelihood and Bayesian Analysis techniques.Finally,by these data to revise and improve the taxonomy of Neidium.The main results are as follows:1.Through literature review,87 taxa of the genus Neidium were reported in China,which includes 48 species,28 variety and 11 form.We have systematized some useful information of Neidium Pfitzer in China,including morphological description,habitats,distribution sites and so on.2.There are 26 species in China with 11 uncertain species among those samples which we collected.3.In this paper,the phylogenetic trees of different species of Neidium were constructed based on the rbc L?psbC and 18 S r DNA sequences data using ML?BA and NJ methods.The main results are as follows:(1)The phylogenetic analysis based on rbc L and psbC genes revealed that The genus Neidium,Scolioneis kozlowii,Scoliopleura peisonis and Luticola were clustered in a large branch,which revealed a close relationshipbetween them.(2)The phylogenetic tree based on a concatenated alignment of rbc L and 18 S sequences revealed Scolioneis kozlowii and Scoliopleura peisonis were individually in a clade.,thus it can be seen that there was a close relationship between those two species.The classification standard of the genus Scolioneis was verified based on characteristics of the morphology,molucular biology data and ecological habitats.S.kozlowii,S.kozlowii var.genuinum,S.kozlowii var.undulate,S.kozlowii var.elpatievskyi f.majorius and S.undulatum are divided into the genus Scolioneis.(3)The phylogenetic analysis based on rbc L and psbC genes revealed that Neidium cuneatiforme and N.dubium were clustered in a branch.And the p-distance between them was greater than other groups of the genus Neidium.Morphologically speaking,those two species' proximal raphe ends are straight not curved in different direction.which is an important feature in the development of the diatom system of the genus Neidium combining with molecular biology data.