Ringneck snakes are elegant little reptiles distributed across much of the United States, from the Atlantic to the Pacific. In most cases they can be identified by the eponymous band of color encircling their necks. They also exhibit considerable variation in color pattern and size across their geographic range. The two images below provide a sampling of this diversity.
First we see a Northern Ringneck Snake from Allegany County, New York. Ringneck snakes from this region have a slate gray dorsal color with a pale yellow neck band and belly coloration.
Compare that to the Pacific Ringneck Snake from Napa County, California. These Ringneck Snakes have a much darker orange (sometimes almost red!) neck band and belly coloration, and their dorsal gray includes a hint of blue.
What is the cause of this variation? A paper published by Fontanella et al. in 2008 in the journal Molecular Phylogenetics and Evolution provides some clues. They examined variation in mitochondrial DNA of over 250 Ringneck Snakes distributed across their geographic range. Their results indicated a dynamic history for Ringneck Snakes, with 14 distinct genetic groups that are often geographically isolated from one another. Ringneck Snakes currently found along the Gulf Coast may have been separated from the rest of the Ringneck Snakes in North America for several million years. However, the Ringneck Snakes found in the more northern part of their range are recent arrivals, having emigrated North as glaciers retreated and the climate changed over the last 10,000 years; there appear to have been four distinct northern migrations. Although these results are exciting, the authors cautioned that more data is necessary to confirm the results.