Calibration Of Anatidae Molecular Clocks

Mitochondrial cytochrome b(Cyt b) gene were sequenced in 44 geese of Chinese domestic geese(15 breeds) and European domestic geese(2 breeds). Anatidae molecular clocks was calibrated with 2 consensus sequences which come from Chinese domestic geese and European domestic geese and 13 sequences obtained from GenBank. After two-cluster testing,branch length testing and relative rate testing ,two sequences(Melantitta nigra and Aythya americana) of 15 Cty b sequences were deleted because thek evolutionary rate were heterogeneous. The divergence between Anseriformes and Galliformes was chosen as an anchor point. Nucleotide sequence and amino acid sequence of 13 sequences data set was used to calibrated Anatidae molecular clocks. The results indicated that amino acid sequence is better than nucleotide sequence when divergence time is calculated with two kinds of sequences. The reliable divergence time of Anatidae were estimated with "1+2TiTv" model. Two distance models of amino acid sequence could be used to calculated Anatidae molecular clocks and their result are accurate. The estimation of the split between Phasianidae/Anatidae is 116.3785MYA (" l+2TiTv"). The divergence time of Anser/Anatinae is estimated to be 71.2247MYA(" l+2TiTv"). The origin of two basal groups took place in the Cretaceous. This result is consistent with the early history of avian occurred in the Cretaceous(l 10-66MYA).