Great Basin Naturalist


Population density, reproduction, and survivorship were compared between 2 populations of Sceloporus grammicus occurring at different altitudes (3700 m and 4400 m) on the eastern slopes of Iztaccihuatl Volcano, Puebla, México. Lizards in both populations matured at the same age (14–15 mon) and size (39–42 mm SLV). Population density was slightly greater at high altitude (131–163 per ha) than at low altitude (52–83 per ha). Survivorship and Ro were higher at the low-altitude area, but in general there were no significant demographic variations between altitudes that have been reported in lizard population at higher latitudes. Studies of lower-elevation populations might reveal some differences because previous studies indicate that litter size increases at lower altitudes, although they do not differ between our 3700 m and 4400 m populations.