SPECIES do not always arise by new branches forming on the family tree. Sometimes the branches merge, and two species hybridise to form a third.
Such hybrid speciation has previously been reported in plants, but never conclusively in animals. Now a study of butterflies has revealed that a wild species of the brightly coloured Heliconius butterfly in South America arose via the merger of two related species. What's more, something resembling this species can be artificially created in the lab.
Heliconius cydno, a butterfly that lives in the mountains of eastern Colombia, bears dramatic yellow bands across its forewings. Its close relative, Heliconius melpomene, has wings with bright red bands. A third species, Heliconius heurippa, which has both yellow and red bands, has often been suspected to be a hybrid of the two.
H. heurippa can only be described as a species in its own right, rather than just a ...
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