Sauromalus ater

Hollingsworth (1998) examined variation in Sauromalus and concluded that five species should be recognized. He regarded S. obesus as conspecific with S. ater, and he used S. ater, which has priority, as the specific name of the combined taxon. No subspecies of S. ater were recognized. Based primarily on the extensive use of the name S. obesus, a petition to give that name precedence over that of S. ater was submitted to the ICZN. However, McDiarmid et al. (2002) questioned this reasoning and argued that the priority of S. ater should be maintained. ICZN (2004) ruled that the name Sauromalus ater Duméril 1856 has precedence over the name Sauromalus obesus (Baird 1858). Hence, Sauromalus obesus is no longer the correct name for the chuckwallas of the United States (or Mexico).

Although all mainland populations of Sauromalus are currently considered to constitute a single species, intergradation or the lack thereof between divergent mtDNA haplotype clades (Petren and Case 2002) deserves further study (Crother 2017). See Petren and Case (1997) for a phylogenetic analysis of Sauromalus based on mtDNA variation. Patterns of mtDNA variation show geographic patterns but do not exhibit a phylogenetic break at the Colorado River valley (in contrast to the pattern found in the desert tortoise) (Lamb et al. 1992).

MtDNA data indicate that Cyclura is monophyletic and not closely releated to any other genus, whereas Iguana is strongly supported as the sister taxon to Sauromalus (Malone et al. 2000). Wiens and Hollingsworth (2000) concluded that Cyclura is the sister taxon of Iguana and that Sauromalus probably is the sister taxon of the Cyclura-Iguana clade.

Fairly common in many areas in a restricted range in the deserts of southwestern North America; little information is available on populations and trends, but apparently secure rangewide; threatened by collecting in some isolated areas, but probably not very threatened rangewide.

This lizard ranges from southern Nevada, southern Utah, southeastern California, and western Arizona south to southern Baja California and west-central Sonora, Mexico; in Baja California, most of the distribution is away from the west coast (Hollingsworth 1998, Grismer 2002, Stebbins 2003).

This species is represented by a large number of viable occurrences throughout the majority of the range in California, Arizona, and Sonora, Mexico.

Chuckwall populations are locally threatened by excessive collecting and habitat degradation (New Mexico Department of Game and Fish 1997). Collectors not only remove individuals from the habitat may thus may reduce population viability but also often cause microhabitat destruction when tools are used move or break rocks and exfoliations to expose the reptiles (New Mexico Department of Game and Fish 1997). Some populations have been hard hit by collectors. For example, the easily accessible South Mountain population, near Phoenix, Arizona, has a unique color pattern and is highly desired by the pet trade; exploitation of this population and destruction of its habitat are on the rise (Gergus et al. 1998). Historical populations in the Glen Canyon area of Utah have been reduced or eliminated by the damming of the Colorado River. Habitat degradation due to grazing activities of goats, sheep, and burros is also a potential threat.

Overall, however, the species appears to be moderately to not very threatened across most of its range. The species is regarded as not very threatened in Sonora, Mexico (Andres Villareal Lazarraga, pers. comm., 1998).