Study On Relationships Between DNA Coding And Phylogeny Of Ursidae

With the development of molecular biology, traditional classification has brought through the longtime standstill and begins to come into the molecular stage. Since the concept of DNA barcode was first proposed, DNA barcoding has been proved that it is an effective mean of biological identification now. It plays an important role in the development of biological protection and biodiversity. Besides it solves the problem of identification, it also supply the available "leaves" for the construction of phylogeny tree so that it push the research of biological evolution history.Bear family(Ursidae) belongs to carnivora, mammalia, subphylum vertebrata, chordata. The differentiation of bear family that spends short interval time is a rapid affair of evolution radiation and species forming. There are disputes in the phylogenetic relationships of Ursidae species all the time. Because of the humans hunting and the destruction of habitants, the population of Ursidae species decrease sharply and all species of Ursidae have been listed as the national endangered. protected species. In order to deal with the phylogenetic relationships of bears species as well as the evolution and classification, fight against the crimes and offer the technical support for protection and management of bears, Ursidae species were coded by DNA barcoding technology and phylogeny trees were constructed with COI,12SrRNA and Cytb Gene.Thirty two COI sequences of Asian Black bear, and five Cytb and 12SrRNA sequences of Asian bear and brown bear respectively were obtained. The analysis showed that there are some bias in base components of COI,12SrRNA and Cytb genes of bear family. The content of A+T is more than that of G+C.Phylogeny trees show that brown bear and polar bear is a sister group, American black bear has a close relation with brown bear and polar bear, but has a distant relation with Asian black bear. Asian black bear should belong to black bear genus Selenarctos independently, and not to bear genes Ursus. While American black bear, brown bear and polar bear should belong to bear genus Ursus. Sun bear has a close relation with American black bear while has a distant relation with sloth bear whose differentiation is earlier than Sun bear. Giant panda and spectacled bear are the earlier diverged species of bear family. Red panda does not belong to Ursidae. Tibet blue bear is a subspecies of brown bear and shouldn't be classified as a single species.Phylogeny trees of COI genes have consistent with the tree of combined data on species level. COI gene as DNA barcode is more effective than 12SrRNA gene and Cytb gene on subspecies level. Sequence divergences of intraspecies and interspecies for brown bear and polar bear are very small based on COI,12SrRNA and Cytb gene. When species identifications of brown bear and polar bear are made, it is not enough to rely on sequence differences and phylogeny trees and the conclusion should be made with others analysis method.