Sequences Variation Of Mitochondrial 12s Rrna Gene And Molecular Phylogeny Of 20 Species Birds(aves: Charadriiformes)

Charadriiformes is a most important component of the Wetland ecosystem, and it has very important ecological significance. One of the main problems to controvert in avain reseach is about the classification of the family and higher level in this group. The previous researches are almost based on morphology and ecology. There is disputation about the classification based on morphological traits, because of the great similarity (convergence) in morphology, habits and other aspects among many species of Chrardriiformes. Therefore, it is necessary to study the relationships among the group using molecular biology method.Using the well-known PCR techniques, the complete mitochondrial 12S rRNA gene sequences were amplified and sequnced from fifteen spices belonging to 4 families. Sequence analysis was made using these 15 sequences combining the corresponding sequences of five species downloaded from Genbank, and phylogenetic trees weae constructed. That provides a certain evidence to illustrate the phylogenetic relationships of this group. The results show that:1. The characteristics of complete 12S rRNA gene sequences (1031bp) are as follows: average base frequencies of T, C, A and G are 21.4%,26.9%,31.4% and 20.2% respectively; The content of purine bases is 51.6%, a little higher than that of pyrimidine bases. Transtions and trsversions are the major type of nucleotide substitutions and the number of transitions is larger than that of transversions, the average ratio of transitions to transversions is 3.3. The average genetic distance in all sequences is 0.115.2. The phylogenetic tree reconstructed is composed of three clades: one is Scolopacidae, one is Laridae and Alcidae, and another is Charadriidae. Charadriidae lies on the bottom of the tree, and it is the first clade diverging from the ancestor.3. When Scolopacidae was analysed individually, Limicola falcinellus always lies in genes Calidris either in NJ trees or in MP trees, so it is doubted that Limicola falcinellus is a mumber of the genus Calidris.4. 12S rRNA gene sequence is abundant of variation; the complete sequence contains evolution information from interspecies to interfamily. Reconstructed phylogenetic tree applying this gene is different from those applying morphological traits. And it can provide molecular evidence to study the phylogeny of this group.From the result, we can conclude that:1. Among the six families researched, Charadriidae is the most primordial family, and it is the first fimily divergenced from ancestor. Laridae, Stercorariidae, Sternidae and Alcidae make up of Laridea. The last one divergenced is Scolopacidae.2. In Scolopacidae, the genus Calidris convergenced uppermost.3. In the family Scolopacidae, Limicola falcinellus always lies in genes Calidris, which implies that Limicola falcinellus shold be included in genes Calidris. Genus Tringa and Calidris gather a cluster, which implies that these two genus have close relativeness.4. In family Charadriidae, Charadrius alexandrinus and Charadrius dubius of genus Charadrius cluster first, then gather with Pluvialis fulva of genus Pluvialis. All of this shows that the molecular relationships between species of family Charadriidae in this study is in highly accord with that of morphology.