The Greenish Warbler was long considered an idealized example of a single species, which diverged into two and expanded its range. It has been found that this species has a much more checkered family history than biologists previously realized. Ring species are a continuous loop of related populations, each adapted to its local environment, with two terminal populations in the loop meeting but now unable to mate. But an in-depth genomic analysis published today in Nature by University of British Columbia researchers reveals that the Greenish Warbler's genetic migration through central Asia involved periods of geographic separation and hybridization.
"We've shown that the evolution of ring species is much more complex than the smooth and continuous divergence envisioned by the classic model," says UBC zoologist Miguel Alcaide, the paper's lead author.