Is it reasonable to do positive selection among several anciently diverged species? Take insects for example. Some insects were reported to diverge around 500 million years ago. Can we get meaningful results of positive selection using this kind of data?
What do you mean by "Is it possible to do positive selection"?
@Niek: I have changed the word to "reasonable" to put my idea more clearly. We can always do the analysis with the data. But garbage in,garbage out. If the data is not suitable for this analysis, the result will be meaningless.