REPRODUCTION OF THE VIVIPAROUS LIZARD LIOLAEMUS-ELONGATUS IN THE HIGHLANDS OF SOUTHERN SOUTH-AMERICA - PLASTIC CYCLES IN RESPONSE TO CLIMATE

Squamate viviparity has evolved on several occasions, and probably ind ependently within the genus Liolaemus itself. Hypotheses about the ori gin of reptilian viviparity emphasize the advantage of providing an ad equate thermal environment for the embryo. At the same time, high lati tudes and altitudes limit the availability of heat to perform vitellog enesis and gestation. The genus Liolaemus includes both oviparous and viviparous modes of reproduction, as well as reproductive cycles with great variations in the timing of the events. In the present work maxi mum juvenile size, sexual dimorphism, gonadal cycle and litter size of viviparous Liolaemus elongatus were studied. Female lizards may have annual or biennial cycles, but males reproduce annually in synchroniza tion with the female cycle. Phenotypic plasticity may be one way that allows the species to cope with environmental constraints, and may be a reproductive adaptation that Liolaemus has evolved in response to th e the cold climate in the highlands of southern South America.