A Study On DNA Barcoding And Molecular Phylogeny Of Chinese Unionidae

Freshwater mussels are widely distributed in the streams,rivers and lakes,and play important roles in freshwater ecosystem.The species of freshwater mussel are very rich in the middle and lower reaches of the Yangtze River basin in China.Impacted by habitat degradation and destruction,pollution,over-exploitation,anthropogenic disturbances and other natural factors,the population of mussels is seriously declined and many species are thought to be endangered.Traditionally,the identification and classification of mussel mainly relied on morphological characteristics of the shells,but to some extent,the shapes of their shells are plasticity and convergent.There have different views on the families and genera of freshwater mussels of classification.In the present study,including 41 species of 14 genera of Chinese unionids,the species were obtained from the Yangtze River basin.Mitochondrial gene COI and nuclear gene 28 S were selected as the candidate DNA barcoding.First of all,analyze the characteristics of the two candidate genes,and then compared their interspecific and intraspecific difference.Finally,analyzed the phylogeny of unionids by researching the published COI and 28 S sequences of unionoids,aimed to provide molecular evidence for uniodidae classification.The main results are as follows:1.The content of A+T of the COI and 28 S were 58.7% and 34.3%,respectively,and G+C content were 41% and 65.4%,respectively.Mitochondrial gene COI base transition/transversion ratio is bigger than 28 S,and transversion transformation of the two genes are 1.58 and 1.27,respectively.2.The average intraspecific genetic distance of COI is 0.0029,the interspecific genetic distance 0.163;The average intraspecific genetic distance of 28 S rDNA is 0.0006,the average interspecific genetic distance was 0.039,The barcoding gap of COI is significantly larger than the 28 S rDNA,describing that use using COI gene sequences as DNA barcoding is superior to 28 S rDNA sequences.3.COI and 28 S sequence data were also used for the phylogenetic analyses.Chinese unionidae can be divided into two groups(Gonideinae and Unioninae).The species of the Unioninae are abundant,including 10 valid genera,and except for the genus Anodonta,Lanceolaria,the other genera have formed monophyletic group.There are 4 genera in the Gonideinae,and Gonideinae is the sister group to Unioninae.except for the Solenaia,other genera of Gonideinae have formed monophyletic group.4.By phylogenetic analysis,the Lamprotula was found polyphyly and furthermore,Lamprotula rochechouartii was found not belonging to the genus Lamprotula.The results suggested that Lamprotula rochechouartii and Margaritiferidae had a relatively closed phylogenetic relationship.