André Freitas / UNICAMP Melinaea ludovica, a species found in the forests of Brazil, Venezuela, Colombia, and PeruAndré Freitas / UNICAMP
Genome sequencing of butterflies from the Melinaea and Mechanitis genera is revealing the factors behind species diversification. An international group of researchers found that some species arose through hybridization—a process that increased genetic variation—and later became reproductively isolated from their ancestors. Part of this process is identified by differences between species in mitochondrial DNA, of maternal origin, and the nuclear genome. The divergence of species occurred rapidly over less than 2 million years, through chromosomal fusions and fissions. “We still don’t know why this rearrangement occurs more frequently in this group of butterflies, but we observed a significant variation in the number of chromosomes,” says biologist André Freitas of the University of Campinas (UNICAMP), coauthor of the study. Even if they are genetically close, two species with different sets of chromosomes cannot produce offspring when they interbreed (PNAS, July 28).
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