Lampropeltis alterna

Garstka (1982) and Bryson et al. (2007) reviewed the mexicana species group of Lampropeltis. Based on the more recent molecular work, it appears that the recognition of the traditional species of alterna, mexicana and triangulum may be incorrect. Until more data are available to resolve the taxonomy of these groups, Crother (2017) withhold making any changes. Given the apparent complexity of the situation and the widespread morphological variation of L. alterna, Crother (2017) do not recognize any subspecies, though Hilken and Schlepper (1998) argued for recognition of L. alterna alterna and L. a. blairi. Ruane et al. (2014) showed that this is an evolutionarily distinct lineage, and clearly represents a separate species. Previous work showing affinity with L. triangulum based on mitochondrial data was misled by an apparent genome capture (Crother 2017).

Myers et al. (2019) found three unique lineages corresponding to the Trans-Pecos and Mapimian biogeographic regions of the Chihuahuan Desert, and a distinct population in the Sierra Madre Occidental.

The range extends from southeastern New Mexico (Painter et al. 1992, Degenhardt et al. 1996) and southwestern Texas (Werler and Dixon 2000) southward to northeastern Durango and extreme western Nuevo Leon, central Mexico (Stebbins 2003), at elevations of 670-2,286 meters (1,200-7,500 feet) (Werler and Dixon 2000).

This species is represented by many occurrences or subpopulations (e.g., see map in Werler and Dixon 2000). This secretive snake likely occurs in many more localities than are currently known, especially in areas away from roads.

This species is one of the most desirable and sought-after snakes in the commercial pet trade in North America. Collectors perhaps have depleted roadside populations in some areas (snakes found on roads are mostly adult males; see Werler and Dixon 2000). The threat from collection has been reduced somewhat in recent years. Collection without a permit is illegal in Texas and New Mexico. Captive breeding has generated a good supply of animals for the pet trade. Populations away from roads (the majority of the population) presumably are not significantly threatened.