International Study Led by Harvard Scientists Reveals Surprising Amount of Gene Flow Among Butterfly Species, Even Between Some That Are Distantly Related

An international team of researchers analyzed the genomes of 20 butterfly species and discovered a surprisingly high amount of gene flow among them - even between species that are distantly related. The findings, published in the November1, 2019 issue Science, challenge conventional views about species and point to hybridization as a key process in the emergence of biological diversity. The article, which serves as the cover story of this issue of Science, is titled “Genomic Architecture and Introgression Shape A Butterfly Radiation.” Different species of passion vine butterflies (Heliconius) have similar color patterns that serve as warnings to predators. Scientists have previously found that one reason for their similarity is that they actually share parts of their DNA, thanks to hybridization that occurred at some point in their ancestry. The new findings suggest that this process of DNA sharing is far more common than previously thought. To understand how butterflies pass genes to other species by hybridizing, a process known as introgression, the researchers analyzed new genome assemblies of 20 Heliconius butterfly species. "DNA sharing had been shown in closely related species, but we wanted to probe deeper into the phylogenetic tree," said senior author James Mallet, Professor of Organismic and Evolutionary Biology in Residence and Associate of Population Genetics in the Museum of Comparative Zoology. "What we found is really astonishing: introgression even among species that are distantly related. "Species" are simply not what we thought they were, and now we have the data to show it.
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