知识与财富的链接
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。
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.
