Do male and female lizards handle growth challenges differently?

Scientists picked two closely related spiny lizard species to see if sex or birth method makes a bigger difference in how stable their body shapes grow. One species gives live birth and thrives in cool mountain air, while the other lays eggs and lives at slightly lower elevations. Researchers measured tiny twists in head shapes—like whether the left and right sides match perfectly—by plotting 22 precise spots on lizard heads and running shape comparisons. They also looked at how tightly each group kept its ideal head shape under genetic and environmental pressures.Males from the live-bearing species showed stronger shape control than any lizards from the egg-laying group, yet within each species males and females had similar levels of shape wobble. The egg-laying species was actually more variable overall, suggesting its reproductive routine may leave less room for precise sculpting. Surprisingly, no clear head-shape split between males and females turned up in either lizard, hinting that overall size differences don’t automatically create shape differences.