Effects of Elevation on Litter-Size Variation Among Lizard Populations in the<i>Sceloporus grammicus</i>Complex (Phrynosomatidae) in Mexico

Abstract

We examined the effect of elevation on litter-size variation in viviparous lizards of the Sceloporus grammicus complex in 10 states of Mexico. Female snout—vent length (SVL) decreased with increasing elevation, and absolute litter size based on embryos also tended to decrease with increasing elevation. However, after controlling for variation in female body size, we found that litter sizes tended to be relatively larger at higher elevation. Elevation therefore appears to influence litter size in these lizards; however, relatively little of the variation is explained by elevation; thus, other factors are likely making substantial contributions to the observed litter-size variation. The S. grammicus complex appears to be a good model system for examining the underlying causes of geographic and elevational variation in lizard life histories.