Measurements of introgression may be made on scales established by principal components, canonical correlation vectors, discriminant functions, hybrid indices, and a proposed distance analysis. The distance analysis developed is the most sensitive scale used. When the methods were used on a set of data from introgression of two pine species, the failure of some of the assumptions was such as to lead to some differences in biological conclusions
Statistical Analysis of Introgression
Namkoong, G. (1966). Statistical Analysis of Introgression. Biometrics, 22(3), 488-502.