Society for the Study of Amphibians and Reptiles Diet and Reproductive Biology of the Viviparous Lizard Sceloporus torquatus torquatus

-The reproductive cycle and diet of a population of the viviparous lizard Sceloporus torquatus torquatus from the Pedregal de San Angel, Distrito Federal, Mexico, were studied. Ovarian activity began in June, and by October, one to five preovulatory follicles per ovary were present Ovulation took place in November and December, and parturition occurred in late April or early May. Relative litter and egg masses were higher at the end of development than at the beginning. Testes increased in size from June through September, when they reached their maximum volume and weight Testicular regression began at this point and was particularly accentuated in October and November. The diet of both sexes was composed primarily of insects; however, plant material (small flowers and fruits), spiders, isopods, and occasionally earthworms were also consumed. Both sexes consumed plant material throughout the year. In the dry season, males ingested twice as much food as females. RESUMEN. -Se estudiaron el ciclo reproductor y la dieta de una poblacion de la lagartija vivipara Sceloporus torquatus torquatus que habita en el Pedregal de San Angel, Distrito Federal, Mexico. La actividad ovarica comenz6 en junio, y para octubre se encontraron de uno a cinco foliculos preovulatorios por ovario. La ovulaci6n ocurri6 entre noviembre y diciembre, y el parto a fines de abril o principios de mayo. La masas relativas de la camada y de los huevos fueron mayores a finales del desarrollo embrionario que al principio. Los testlculos aumentaron de tamafno desde junio hasta septiembre, cuando alcanzaron su volumen y peso maximos. Posteriormente comenzo la regresi6n testicular, la cual fue particularmente acentuada en octubre y noviembre. La dieta de ambos sexos consisti6 principalmente de insectos; sin embargo, tambien se consumieron, ademais de materia vegetal (flores y frutos pequefios), arafias, is6podos y ocasionalmente lombrices de tierra. Ambos sexos consumieron materia vegetal durante todo el afo. En la epoca seca, las hembras consumieron alrededor de la mitad del alimento consumido por los machos. Fitch (1970) stated that the reproductive season in temperate lizards usually occurs during the spring and summer. However, reproductive patterns in which gametogenesis, courting, copulation, and fertilization occur in the fall have been reported since the early 1970s (Goldberg, 1971; Ballinger, 1973). Guillette and Casas-Andreu (1980) pointed out that fall reproductive activity is common in viviparous lizards inhabiting high elevations in temperate zones. More recent papers have reported this reproductive modality in additional species and have attempted to explain its advantages (Guillette and Bearce, 1986; Guillette and Casas-Andreu, 1987; Ramfrez, 1991; Guillette and Mendez de la Cruz, 1993; Ramfrez-Bautista et al., 1996, 1998). Intraand interspecific variation in reproduction and life-history traits of lizards is partially explained by the physical environment (Benabib, 1994). However, it has been shown that factors such as phylogenetic inertia (Ballinger, 1983), foraging behavior (Vitt and Price, 1982), predator escape behavior (Vitt and Condgon, 1978), and individual morphology (Vitt, 1981) can be important in molding the reproductive biology of lizards. It has been suggested that differences in life history within a species may be the result of physiological or developmental responses to environmental conditions, rather than phylogenetic effects or genetic sources (e.g., Steams, 1980). Thus, a better understanding of the influence of envionmental conditions in molding life-history traits requires knowledge of their variation among populations of the same species. Sceloporus torquatus torquatus is a viviparous lizard occurring in central Mexico (Smith, 1936). It is usually confined to rocky habitats, although it is entirely arboreal in some areas (Smith, 1936; Duellman, 1961). Werler (1951), Fitch (1970), and Feria-Ortiz (1989) provided some data on its reproductive biology. Uribe-Alcocer et al. (1995) described the histological changes exhibited by the ovaries in the female reproductive cycle. This content downloaded by the authorized user from 192.168. 52.76 on Mon, 10 Dec 2012 13:41:45 PM All use subject to JSTOR Terms and Conditions DIET AND REPRODUCTION OF SCELOPORUS TORQUATUS