Female reproductive biology of the lizards Liolaemus sarmientoi and L. magellanicus from the southern end of the world.

Lizards that live in the harsh climate of the Argentinean Patagonia (40°-53° S) are active for a period restricted to spring and summer when vitellogenesis, pregnancy and birth take place. Herein, we present data on the female reproductive cycle, body size at sexual maturity, litter size and fat-body cycle of one of the world's southernmost reptiles, Liolaemus sarmientoi. We also provide preliminary data on the reproductive cycle of a sympatric species, L. magellanicus. Females of both species start vitellogenesis in late spring, probably arrested or continued at very low rates during brumation resumed in the spring of the next year. Pregnancy starts in spring and births of L. sarmientoi (2 to 7 offspring) and L. magellanicus (3 to 4 offspring) occur over a month in midsummer. Females that give birth earlier can start a new vitellogenic cycle before autumn and perform an annual reproductive cycle. However, females which give birth later delay the start of a new vitellogenic cycle until the next spring, performing a biennial reproductive cycle. Thus, females have the potential to adjust their frequency of reproduction according to the energetic restrictions imposed by environmental conditions in the southernmost lands of South America. [ABSTRACT FROM AUTHOR]