Pantherophis obsoletus

Based on the congruence of morphological (Burbrink 2001) and mitochondrial data (Burbrink et al. 2000), Burbrink divided P. obsoletus into three species (P. alleghaniensis, P. obsoletus, and P. spiloides) with no subspecies.

Utiger et al. (2002) examined mtDNA variation in New World and Old World "Elaphe" and determined that North American rat snakes currently included in the genus Elaphe form a monophyletic limeage that is distinct from Old World snakes that also have been regarded as Elaphe. They resurrected the genus Pantherophis for the rat snakes north of Mexico, including the following species: Pantherophis obsoletus (and P. alleghaniensis and P. spiloides, if one recognizes those taxa as species), P. guttatus, P. emoryi, P. vulpinus, P. gloydi, and P. bairdi. Based on mtDNA and nuclear DNA data, Burbrink and Lawson (2007) determined that New World Elaphe are not closely related to Old World Elaphe. While further splitting of Pantherophis has been proposed (Collins and Taggart 2008), the use of Pantherophis has helped stabilize the classification of New World ratsnakes. Thus, Crother (2017) refrain from further division of the genus.

Large range and many collection sites and locations in central North America; can be common in altered rural habitats; presumed large population size; likely relatively stable or slowly declining; no known major threats.

As defined by Burbrink (2001), this species occurs west of the Mississippi River, from southern Louisiana along the Gulf Coast to southern Texas, west to central Texas on the Edwards Plateau, and northward through Oklahoma, central and eastern Kansas, southeastern Nebraska, and southeastern Iowa to extreme southeastern Minnesota.

The number of distinct occurrences has not been determined using consistent criteria, but this species is represented by a very large number of collection sites and locations (as defined by IUCN).

Intensive agricultural development and urbanization likely have caused localized declines, and collectors probably have depleted some easily accessible populations, but in most areas this snake is not threatened by these factors. As of 2016, this species was not known to be significantly affected by snake fungal disease.