The use of a pair of populations removes the problems posed by a structured phylogeny (pointed out by A. Robertson) and permits the application of the original test of Lewontin and Krakauer . In the case of 2n populations studied a suggestion is made to use only n pairs in such a way that no population appears in more than one pair. Data on Dacus analyzed this way show that at least two out of six genes studied are or have been selected.
展开▼
