Pantherophis Obsoletus - Taxonomy

Taxonomy

This species has previously been placed (and is still placed by many) in the genus Elaphe, as Elaphe obsoleta. However, Utiger et al. found that Elaphe as broadly construed is paraphyletic, and placed this species in the genus Pantherophis. In addition, because Pantherophis is masculine, the specific epithet becomes the masculine obsoletus. The split of Pantherophis from Elaphe has been further confirmed by additional phylogenetic studies.

In 2001, Burbrink suggested this species be divided into three species based on geographic patterns of mitochondrial DNA diversity. He assigned new common names and resurrected old scientific names, resulting in the following combinations: eastern ratsnake (Elaphe alleghaniensis, now Pantherophis alleghaniensis), central ratsnake (Elaphe spiloides, now Pantherophis spiloides), and western ratsnake (E. obsoleta, now P. obsoletus). However, these three species are not morphologically distinct and overlap in all examined morphological characters. More recent investigations have indicated P. alleghaniensis and P. spiloides interbreed freely in Ontario.

In 2008, Collins and Taggart resurrected the genus Scotophis for Burbrink's three taxa, i.e., (Scotophis alleghaniensis), (Scotophis spiloides) and (Scotophis obsoletus) in response to the findings of Burbrink and Lawson, 2007. The justification for this nomenclatural change has been removed by more recent research.