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Despite swapping DNA through interbreeding, butterflies and other animals can maintain distinct species.
A large new study of ovenbird lineages questions the extent to which competing species push each other to evolve.
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A large new study of ovenbird lineages questions the extent to which competing species push each other to evolve.](https://d2r55xnwy6nx47.cloudfront.net/uploads/2014/03/17974_Campylorhamphus_trochilirostris1-520x325.jpg)