Likelihood ratio tests and maximum likelihood estimates of dN/dS for six Drosophila species of the melanogaster group.

Abbreviation: LRT, Likelihood ratio test.1M1a: ω0 varies between 0 and 1 whereas ω1 = 1;2M2a adds to M1a, ω2>1, which is estimated from the data;3proportions of sites under ω0, ω1, and ω2.4Tests whether the dN/dS relative to the two partitions are significantly different from each other.缩写说明：LRT，即似然比检验（Likelihood ratio test）。1. 模型M1a：ω0的取值区间为0至1，而ω1固定为1；2. 模型M2a：在M1a的基础上新增了ω2>1的位点类别，其参数值由实验数据估算得到；3. 三类位点的占比分别适配ω0、ω1与ω2的选择压力参数；4. 检验针对两个序列分区的dN/dS（非同义替换速率与同义替换速率的比值）是否存在显著差异。