Comparative Demography Of The High-Altitude Lizard, Sceloporus Grammicus (Phrynosomatidae), On The Izthccihuatl Volcano, Puebla, Mexico

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, Mexico. 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 R-o 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.