Complete genomic characterization of butterflies in the United States and Canada. Lepidoptera

The deluge of genomic data will transform biodiversity research by connecting organismal and molecular evolution. Here, we sequence genomes of 845 butterfly species recorded from nearly the entire Nearctic ecozone. Our comprehensive approach reveals an uneven pattern of organismal evolution manifested in drastic differences in speciation and evolutionary rates between lineages. Additionally, radiations in many lineages during the last 5 million years are associated with elevated divergence of genes involved in transcription, morphogenesis, and neurological processes. This higher divergence is likely caused by relaxed purifying selection and more frequent introgression of such genes in radiating lineages. Finally, during the last 100 million years, the evolutionary rate differed between genes by several orders of magnitudes, and both selection pressure and introgression might have contributed to such differences. These observations suggest the critical role of introgression in butterfly evolution, which may stimulate radiation and allow a species to survive harsh conditions by gathering beneficial genes from its relatives.