How new characters originate and evolve is one of the outstanding problems in evolutionary biology. Recent genomic data suggests that characters that evolve within one lineage can sometimes spread to other populations with limited genetic exchange, resulting in asymmetric introgression and a mosaic genome in the receiving population. However, only rarely are systems sufficiently well understood to predict the degree and direction of hybridization, which limits our ability to interpret genomic signatures of introgression. Male common wall lizards in western Italy exhibit exaggeration of a suite of sexually selected characters, including morphology, colouration and behavior. These characters allow them to outcompete males from other lineages that lack these characters. We have shown that this results in asymmetric hybridization and adaptive introgression of the suite of characters following secondary contact. Our current research, funded by the Swedish Research Council, is extending this work in several directions. Our aims are to test if genomic and developmental modularity facilitated the evolutionary origin and adaptive introgression of this suite of characters, and to identify what – if anything – that limits introgression and how repeatable this evolutionary process is across different contact zones.