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Now One, Quoth the Raven

Two once separate species of ravens have formed a single species in an instance of species reversal, according to a new study.

Researchers from the US and Norway conducted a phylogenetic analysis of raven lineages in North America to untangle how they are related. Study author Kevin Omland from the University of Maryland, Baltimore County, tells the Guardian that he'd suspected that ravens in the region belonged to two lineages, California ravens living in the southwestern US and Holarctic ravens that live elsewhere.

As he and his colleagues report in Nature Communications, they found that Common Ravens, Corvus corax, are the result of admixture between the non-sister California and Holarctic raven lineages. The two lines separated about 1.5 million years ago, but interbred tens of thousands of years ago. Pure California ravens no longer exist.

"The extensive genetic data reveals one of the best supported examples of speciation reversal of deeply diverged lineages to date," co-author Arild Johnsen at the University of Oslo tells the Guardian. "The biggest thing is the degree to which we've caught them in the act."

At the same time, the researchers report that Common Ravens and Chihuahuan Ravens (C. cryptoleucus), despite their overlapping ranges, are reproductively isolated.