Ontogenetic Shifts of Morphology and Food Habits in the Oriental Garden Lizard,Calotes versicolor (Agamidae)

Males and females of the oriental garden lizard (Calotes versicolor) from a population in Tongshi,Hainan,southern China,differ in head size at hatchlings,with males having larger heads than females.This sexual dimorphism is slightly more pronounced in adults than in hatchlings.Embryos of C.versicolor allocate relatively more resources to the growth of ecologically significant morphological characters than do characters less directly tied to early survival and growth of hatchlings.As a consequence of this allocation pattern,hatchlings have larger heads but shorter tails relative to snout-vent length (SVL) than do juveniles and adults.Adults do not show a sexual dimorphism in SVL,but male adults attain longer tails than do female ones at the same SVL.An isometric growth pattern with SVLs increase is showed in the head length of both sexes and the head width of females during ontogeny.However,an allometric growth pattern with SVLs increase is showed in the head width of males,which the growth rate becomes increasingly fast with the ontogeny.The food niche width and overlap differ in the different age and sex groups to a certain extent.However,no direct evidence has been found to show a noticeable contribution of the divergence in head size to the food niche segregation between males and females.