Variation in reproductive traits within the lizard genus Xenosaurus

Abstract

We document variation among 13 populations of distinct species of the lizard genus Xenosaurus in four key reproductive traits: minimum size at maturity, litter size, size at birth, and relative clutch mass (RCM). Despite a common flattened morphology, considerable variation occurs in the examined traits. Minimum size at maturity varied between 92 and 110 mm snout–vent length (SVL), average litter size ranged between 2.1 and 5.7 newborns per female, mean size at birth varied between 40.6 and 51.6 mm SVL, and average RCM ranged between 0.16 and 0.35. We also found considerable interpopulational variation in mean size of reproductive females (from 102.9–119.2 mm SVL) and in the length of the birth season (from about one month to four months distributed between early May and late September). Litter size and RCM were the most variable traits with coefficients of variation above 20, whereas the other traits showed coefficients of variation between 4 and 7.4. Only the minimum size at maturity showed an allometric effect. Litter size and size at birth were negatively correlated, which we interpret as evidence of a trade-off between these two traits. Cluster analyses revealed the existence of two main life-history strategies: populations with relatively large litters of small young and populations with small litters of large young. We suggest further ecological and phylogenetic analyses to explain the patterns of variation and covariation observed in the studied traits.