Evolutionary, ecological, and morphological distinctiveness of an endemic Arizona lizard, Pai Striped Whiptail (Aspidoscelis pai)

The distribution of Pai Striped Whiptail (Aspidoscelis pai) includes much of north-central Arizona in its hypothetical geographic range. However, during a systematic survey across the northern third of the state in 2000-2010, we found it at relatively few sites, and primarily in Plains and Great Basin grassland biomes at elevations between 1600 and 2000 m. Evidence of habitat disturbance was typically apparent (i. e., road corridors, livestock grazing, livestock trails, and/or relocation of rocks). Based on 40 specimens from four areas in Coconino and Gila counties, including 11 gravid females to 72 mm snout-vent length (SVL) with a mean clutch size of 3.2 (range: 2-4) and several males to 71 mm SVL, we found no support for reports of maximum SVL in either sex of 78-85 mm. Whereas the original description of A. pai was based on data for five characters in one sample, we present data on 10 characters in four samples. We compared A. pai with its Arizona close relative, A. arizonae, which is restricted to parts of Cochise and Graham counties. Although it is an oversimplification to state that A. pai is a six-striped species, because an indistinct vertebral stripe is often present, we agree that A. pai and A. arizonae are distinct historical entities based on significant differences in six meristic characters and distinctive color patterns throughout ontogenetic development.