Species Validity Analysis Of Genus Anodonta (Unionidae) And The Phylogenetic Study Based On DNA Barcoding

Freshwater mussels are widely distributed in the global freshwater basins except the Antarctic pole.As the important economic value,ecological impact and the distinct life history,it has already attracted great attention to study,and have crucial research potential.China is one of the world's distribution centres of freshwater mussel,especially the middle and lower Yangtze River.Recently,the species diversity is declining resulted from many reasons such as the environmental degradation,habitat reduction,impact from human activities.It is said that 70%of North America freshwater mussel considered extinct,endangered,threatened or of special concern,that required correct preservation strategies.From the point of conservation biology,only clear species classification can ensure the conduction of correct protection methods.Traditional species identification mainly rely on the shell morphology,but the shells are easily changed with the outer environment,the convergent evolution also brings difficulties for classification,particularly genus Anodonta,which have so flexible Phenotypic plasticity and variable shell shape that are treated as one of the most thorny group by conchologist.Many Anodonta specimens were collected from JiangXi and the surrounding waters.Three mitochondrial genes,ND1?CoI?COII were selected as the candidate DNA barcoding to analyze the sequence characteristics and compare their inter-and intraspecific difference,construct phylogenetic trees based on ML?MP and BI methods.Then combined with other related sequences from the subfamily Anodontinae to discuss the phylogeny of genus Anodonta,aims to provide molecular evidence for Anodonta classification,main results are as follows:1).Based on the topological structure of phylogenetic trees and law of DNA barcoding,12 morphological species were reclassified as 6 valid species that are Anodonta elliptica comb.nov.,Anodonta woodiana comb.nov.,Anodonta arcaeformis comb.nov.,Anodonta angula,Anodonta lucida and Anodonta shangraoensis nov.;2).A new species Anodonta shangraoensis was found,named from the collection place.This population that contains 7induviduals has great difference from other certain species,and they gathered as one cluster in the phylogenetics trees,with the addition of significant interspecific distance,they are treat as a new species.3).Two individuals that can't be identified from the shell morphology were classified as Anodonta elliptica applying the DNA barcoding,as the small intraspecific distance(0.003)and the aggregation with Anodonta elliptica in the phylogenetics trees.Meanwhile,Anodonta joreti was combined with Aondonta woodiana elliptica,the valid species name was Anodonta elliptica.Anodonta arcaeformis?Anodonta arcaeformis flavotincta?Anodonta euscaphys?Anodonta fluminea and Anodonta globosula were combined to Anodonta arcaeformis.4).All of the three candidate DNA barcoding,ND1?COI?COII can be used as DNA barcoding for genus Anodonta as they can distinguish the species well.But from the point of the amplification effect,ND1 is better than the other two.Meanwhile,ND1 gene has greater interspecies and smaller intraspecies difference than COI and COII,so,ND1 is more suitable for Anodonta DNA barcoding.