Evaluates "patterns of introgression across the hybrid zone for 13 diagnostic X-linked loci with known chromosomal positions using a maximum likelihood model". Finds different patterns. Correlates cline width and cline center at different loci.
R. Cianchi, A. Ungaro, M. Marini, and L. Bullini. Molecular Ecology, 12 (6):
1461-1471(2003)In swallowtails, uses "nine fully diagnostic and two differentiated allozyme loci and a mitochondrial DNA marker" to find that "Levels of introgression were low (0–1%) at two sex-linked loci and mitochondrial DNA, limited (0.4–2%) at three autosomal loci coding for dimeric enzymes, and high (up to 43%) at four autosomal loci coding for monomeric enzymes."
Hybrids were identified by morphology. Deduction of introgression was based on seeing mixed types in one species and not the other..