Hi everyone, those of us who identify a lot of Sceloporus lizards are well acquainted with the uncertainty surrounding the ranges of the four fence lizard species that used to all be part of Sceloporus undulatus. These species were split back in 2002, but there’s still a lot of uncertainty about the exact boundaries of the species. The map included in the original paper outlined general species ranges, but didn’t investigate where the species meet, and didn’t include any features beyond state borders, making identification in these untested regions tricky.
I decided to create a Google map to plot out all the samples in the below papers to hopefully create an easier map to reference when trying to identify lizards in this complex. The original 2002 paper doesn’t include exact latitude/longitude coordinates for its samples so I had to estimate where the samples came from based on the information it did provide. In most cases this doesn’t really matter since the samples are very widely spaced, so a “good enough” location still serves its purpose. The supplemental 2007 paper sampled a lot more S. cowlesi and S. tristichus specimens, and did include exact coordinates and one known intergrade zone, so it allowed for a more precise mapping of those two species.
These are the referenced papers:
Adam D. Leaché and Tod W. Reeder, Molecular Systematics of the Eastern Fence Lizard (Sceloporus undulatus): A Comparison of Parsimony, Likelihood, and Bayesian Approaches
Adam D. Leaché and Charles J. Cole, Hybridization between multiple fence lizard lineages in an ecotone: locally discordant variation in mitochondrial DNA, chromosomes, and morphology
And here is the map itself:
The overall S. undulatus complex range was made by basically tracing iNat’s rangemaps for the four species, with some added areas for places with confirmed observations outside of the accepted range. The areas labeled “tested range” are a conservative connect-the-dots around the sampled areas. with the lighter-colored “estimated ranges” places around those tested sites where everyone seems pretty confident what the locally-occurring species is.
The biggest unknown area is most of Mississippi, there’s a known population of Prairie Lizards in the bottom of the state along the Louisiana border but it’s unknown where that population meets the Eastern Fence Lizard. Further north it’s generally accepted the Mississippi River separates the species, although there’s only once tested specimen near the river itself, near St. Louis.
In the west the most contested area is northern New Mexico, though once I plotted everything out on the map it actually proved to be better-tested than I thought. The mountains around Santa Fe and Taos and the top of the state tested pretty strongly as Plateau Fence Lizard territory, though there’s still a large unknown area north of Albuquerque extending almost all the way west to Flagstaff. There was also no clear tested boundary between the Southwestern Fence and Prairie Lizards in eastern New Mexico and western Texas, and a smaller unknown range between the Plateau Fence and Southwestern Fence Lizards northeast of Tucson, but neither of those regions seem to produce as many observations on iNat as that patch of northern New Mexico.
I hope this map can help others identify lizards in this complex. If anyone knows of any other papers that would provide good data to add please let me know. I’m aware of Leaché’s other paper at https://academic.oup.com/sysbio/article/58/6/547/1633600, but the samples he references in that one are the same as in the 2002 paper.