631190-20-5P AID: 2498 | 30/12/2015
The number of nonsynmous species difference is at 7, so the ratio of fixed nonsynonymous species difference is greater than the ratio of polymorphisms. The obtained information tells that selection played a role in the different results. If this number is 1 instead of 7, then the ratio of nonsynonymous to synonymous species difference would be similar to the ratio of nonsynonymous to synonymous polymorphisms, which tells that no selection took place in the observed differences. So, the obtained differences are mere a result of random genetic drift.