Female Reproductive Characteristics among Populations of the Oviparous Lizard Sceloporus aeneus (Squamata: Phrynosomatidae) from Central Mexico

We studied female reproductive characteristics (clutch size, clutch frequency, egg volume, egg mass, and snout-vent length "SVL" at sexual maturity) in five populations of the Mexican endemic oviparous lizard, Sceloporus aeneus, from the Transmexican Volcanic Belt. Adult females showed a range in SVL of 40-60 mm. Mean clutch size was determined by counting vitellogenic follicles or eggs of females during the reproductive season, and was 6.6 ± 1.5 eggs. There was a positive relationship between clutch size and female SVL for all populations collectively. When analyzed by population, however, only two populations showed this relationship. Females lay at least two clutches during the reproductive period (from April to September). We found differences in the mean SVL of females with eggs and vitellogenic follicles among populations, but not in size-adjusted clutch size, egg mass, or egg volume. Our results showed life-history traits (SVL at sexual maturity, reproductive period, clutch size, clutch frequency) similar to those of other populations of this species, and to some small oviparous congeners that produce multiple clutches. Patterns in the relationship between SVL and clutch size were different among the five populations studied, which suggests that more studies on different populations are needed to understand the geographic variation exhibited by these traits. Our observations contribute to the knowledge of variation in the reproductive biology of this species.