Abstract
Natural hybrid zones have provided important insights into the evolutionary process, and their geographic stability/instability over time can help to disentangle the underlying biological processes that maintain them. Here, we leverage replicated sampling of an identical transect across the hybrid zone between yellow-shafted and red-shafted flickers to assess its stability over ~60 years (1955-1957 to 2016-2018). Using a plumage scoring approach that we validate with independent multispectral photography, we identify a ~73 km westward shift in the hybrid zone center towards the range of the red-shafted flicker but no associated changes in width. By integrating previous work in the same geographic region, it appears likely that this movement has occurred rapidly in the years since the early 1980s, prior to which the hybrid zone had remained stable over the previous century. This recent, rapid movement may be related to changes in climate or land management in contemporary times.
Competing Interest Statement
The authors have declared no competing interest.
Footnotes
The authors wish to be identified to reviewers.
