Variation in body size and reproductive characteristics among chromosomal races of the Sceloporus grammicus complex in Mexico

Populations and chromosomal races of a species often show variation in life-history characteristics due to phylogeny and environmental factors. We analysed variation in snout-vent length (SVL) and reproductive variables, such as minimum SVL at sexual maturity, litter size and embryo volume in females of the Sceloporus grammicus lizard complex, which includes seven chromosomal races as well as hybrid zones among different combinations of races (F5, F5+6, potential but unverified F5+6, F6, FM1, FM2, FM2 × F5 hybrid zone, FM3, LS and unverified SGG). The SGG, F5 and LS females were larger than F6 and FM3 females. Females with non-vitellogenic follicles and vitellogenic follicles were smaller than females with embryos. The SVL of females containing embryos varied among chromosomal races, the largest being the same as indicated above, but the smallest was the FM2 × F5 hybrid zone. Litter size was similar among chromosomal races (5.8 embryos), while embryo volumes varied among them. Two patterns of reproductive activity were found: seasonal and continuous reproduction. Our results showed the influence of environmental factors of each locality, which supports the ecological hypothesis. The use of chromosomal races did not reveal a significant phylogenetic effect, because allozyme and molecular data show only small pairwise genetic distances among the S. grammicus populations on the Mexican Plateau.