Reproductive cycle of the spiny lizard Sceloporus jarrovii (Sauria: Phrynosomatidae) from north-central Mexico

We studied the reproductive cycle of Sceloporus "jarrovii" from a temperate environment of the Sierra Madre Oriental in Mexico. Males reached sexual maturity at a smaller snout vent length (SVL; 46 mm) than females (60 mm). Reproductive activity of both sexes was asynchronous, similar to other species inhabiting montane zones. Testes increased in size from June to November and declined rapidly in November. Vitellogenesis occurred from August to October, with ovulation occurring between November and December. Embryonic development was observed from December to early May. There was a significant positive correlation between litter size and female SVL. The reproductive cycle of S. 'jarrovii" is similar to other montane species of several families (Anguidae, Scincidae, Phrynosomatidae). Vitellogenesis, ovulation, and gestation time are shorter in northern (Arizona) than southern populations (Mexico). Females from northern populations are larger in SVL and have larger litter sizes than southern populations. Our study suggests that the montane environment (cool temperatures, short growing season, rainfall during the summer) of S. 'jarrovii" has played a role in the evolution of a set of reproductive characteristics shared by evolutionarily distant viviparous lizard species inhabiting the montane zone.