不同位点碱基替代对标定鸭科分子钟的影响

试验使用GenBank中已知的鸟类细胞色素b(Cyt b)基因部分序列(1044 bp)(共13条序列,其中鸡形目4条、鸭科鸟类9条)作为本研究的数据集,并以鸡形目与雁形目(鸡/绿头鸭)的分歧时间(89.8 MYA)为锚定点,用核苷酸不同替代模型对鸭科的分子钟进行标定。雉科与鸭科间的分歧时间的估计值为116.3785 MYA("1+2TiTv"),雁属与5个鸭属间的分歧时间为63.8823 MYA("1+2TiTv"), 鸡与鹌鹑的分歧时间为37.6708 MYA("1+2TiTv"),灰雁、白额雁与鸿雁间的分歧时间的估计值为1.879331 MYA("1+2TiTv")。以上结果说明:用"1+2TiTv"模型分析得到的鸭科鸟类的分歧时间比较可靠;雉科与鸭科、雁属与鸭属两个接近基部类群的分歧时间发生在白垩纪(137-65 MYA),支持鸟类早期历史发生在白垩纪的观点。

Effects of Different Sites of Base-pair Substitution on Calibration of Anatidae Molecular Clocks

In order to estimate the divergence times of Anatidae and investigate their genetic background,the mitochondrial cytochrome b(Cyt b) gene partial sequences provided at NCBI were totally constructed a 13 sequences database for the next step analyze.The divergence time between Anseriformes and Galliformes was chosen as an anchor point to calibrate the Anatidae molecular clocks using a sequence calibration method.The results showed that the estimation of the divergence time was 116.3785MYA("1+2TiTv") between Phasianidae and Anatidae.The estimation of divergence time was 63.8823MYA("1+2TiTv") between Anser and Anatinae.A divergence of Gallus and Coturnix occurred in 1.879331MYA("1+2TiTv").The estimated divergence time of Anser anser and Anser cygnoidesa was 37.6708MYA("1+2TiTv").The model of "1+2TiTv" was one kind of ideal model.The divergence of the two basal groups(Phasianidae/Anatidae,Anser/Anatinae)took place in the Cretaceous(137-65 MYA).The results were consistent with the view that avian was originated in the Cretaceous.