| Summary: | If evolution was originally depicted as a tree, with different species branching off as new blooms, then new research shows how the branches may actually be more entangled. In "Hybrid speciation driven by multilocus introgression of ecological traits," published in Nature, Harvard researchers show that hybrids between species of butterflies can produce new species that are genetically distinct from both parent species and their earlier forebears. Writing to Charles Darwin in 1861, naturalist Henry Walter Bates described brightly colored Heliconius butterflies of the Amazon as "a glimpse into the laboratory where Nature manufactures her new species." More than 160 years later, an international team of researchers led by biologists Neil Rosser, Fernando Seixas, James Mallet, and Kanchon Dasmahapatra also focused on Heliconius to document the evolution of a new species. Using whole-genome sequencing, the researchers have shown that a hybridization event some 180,000 years ago between Heliconius melpomene and the ancestor of today's Heliconius pardalinus produced a third hybrid species, Heliconius elevatus. Although descended from hybrids, H. elevatus is a distinct butterfly species with its own individual traits, including its caterpillar's host plant and the adult's male sex pheromones, color pattern, wing shape, flight, and mate choice. All three species now fly together across a vast area of the Amazon rainforest. "Historically hybridization was thought of as a bad thing that was not particularly important when it came to evolution," said Rosser, an associate of entomology at the Museum of Comparative Zoology and formerly a postdoctoral fellow both in Mallet's lab at Harvard and in Dasmahapatra's lab in York, UK. Rosser handled the genetic mapping with co-first author Seixas, another postdoctoral fellow. "But what genomic data have shown is that actually hybridization among species is widespread." The implications may alter how we... |