Meeting Abstract
Hybridization between divergent races and species can produce an amazing diversity of novel forms. However, for these novel recombinant forms to become established, they need to encounter ecological settings in which they are sufficiently fit. In Heliconius butterflies, genetic changes at only a handful of color patterning genes have generated a variety of distinctly colored geographic races that form narrow hybridization zones maintained by strong selection. Using whole genome data, we demonstrate that hybridization between the divergently colored races of H. erato in the Guiana shield, H. e. hydara and H. e. erato has resulted in a recombinant phenotype that has become established as a stable population, called H. e. amalfreda, approximately 0.9-1.2 Mya. The H. e. amalfreda wing color pattern originated from introgression of a 7 kb H. e. hydara region into the H. e. erato genomic background near the gene optix. This region likely affects the spatial expression of red pigmentation and contains a block of recently active transposable elements that are perfectly associated with absence of red hindwing rays in H. e. amalfreda. By releasing the H. e. amalfreda form in a hybrid zone where it is not natively present, we demonstrate that individuals with a novel, hybrid warning coloration can have regionally high survivorship, similar to the parental races. This is in agreement with frequency-dependent selection, imposed by predators that learn to avoid these signal, which favors hybrid phenotypes in areas where rates of hybridization are high. These results show how genomic admixture and selection dynamics in hybrid zones can lead to the establishment of novel adaptive forms.
