Genomic Divergence Across The Speciation Continuum In Heliconius Butterflies

The passion vine butterflies (genus Heliconius) are an emerging model system for studying the genomics of adaptation and speciation. Heliconius are renowned for their bright vivid wing color patterns that serve as warnings to predators of their impalpability and that vary dramatically between both within and between species. When different color pattern forms come into contact in nature, they often hybridize. In Heliconius erato there are a series of hybrid zones that span the speciation continuum. On one extreme there are hybridizing races that show little evidence of ecological divergence or reproductive isolation and hybrids are extremely common. On the other extreme there are highly divergent races that rarely hybridize in nature and show strong pre- and post-mating isolation. We sequenced the genomes of individuals with divergent wing color patterns from three hybridize zones that represent distinct stages across the continuum. Our findings suggest that in the earliest stages of speciation, islands of divergence accumulate across the genomic regions responsible for the differences in wing color patterns. However, as speciation proceeds these islands of divergence appear to succumb to the rising sea-level of genome-wide divergence. As our study continues, we aim to further resolve the process of how divergence accumulates and spreads throughout the genome during speciation.