Abstract
The trade-off between offspring size and number is a crucial concept in life-history theory, offering key insights into animal reproductive strategies. Our study examines the relationship between reproductive characteristics, morphological traits, and metabolism in a total of 290 female Phrynocephalus lizards across 10 species. Reproductive, morphological, and metabolic traits were compared by analyzing Phrynocephalus lizard species with viviparous and oviparous reproductive modes. The results show no significant differences in reproductive traits between oviparous (6) and viviparous (4) species. Snout-vent length and standard metabolic rate positively correlated with offspring mass, while no correlation was found with offspring number. The lack of a trade-off between offspring size and number indicates that larger females invest more in offspring mass rather than offspring number. These results, at least in this genus, were inconsistent with the classic prediction that females give priority to adjusting the number rather than the size of their offspring, enabling us to understand the evolution of the reproductive strategy in reptiles.