不同位点碱基替代对标定鸭科分子钟的影响

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

试验使用GenBank中已知的鸟类细胞色素b(Cyt b)基因部分序列(1044bp)(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116.3785MYA("1+2TiTv"),雁属与5个鸭属间的分歧时间为63.8823MYA("1+2TiTv"),鸡与鹌鹑的分歧时间为37.6708MYA("1+2TiTv"),灰雁、白额雁与鸿雁间的分歧时间的估计值为1.879331MYA("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。

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 Anati- dae molecular clocks using a sequence calibration method. The results showed that the estimation of the divergence time was 116. 3785MYA（＂l q- 2TiTv＂） between Phasianidae and Anatidae. The estimation of divergence time was 63. 8823MYA（ ＂1 q- 2TiTv＂） between Anser and Anatinae. A divergence of Gallus and Coturniz 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.