The main results from this study are :
1. Testing for GWH of the rate of introgression is highly robust in an ABC framework.
2. Neglecting the effects of GWH may lead to wrong biological conclusions, while GWH is more likely the general rule than the exception in nature.
3. Between the two Ciona species, GWH of the rate of introgression is leptokurtic (L-shaped), as expected in the final stages of evolutionary divergence, after the build-up of numerous barriers to gene flow throughout the genome.
4. We detected genomic islands of introgression, i.e, genomic regions with a high concentration of loci at which the two species are particularly prone to exchange alleles.