Sexual dimorphism and female reproduction of Phrynocephalus helioscopus( Agamidae)

From May 2013 to May 2014,166 individual specimens of Phrynocephalus helioscopus were collected from the outskirts of Beitun City,Xinjiang Autonomous Region,to study their sexual dimorphism and female reproduction. We measured nine morphological traits of juvenile and adult lizards. Gravid female lizards were used to examine reproduction and to measure morphological traits. The results of t-test showed that juvenile males had a significantly longer snout-vent length( SVL)( P0.05) than juvenile females; and among the adults,the females had a much longer SVL( P 0. 05) than the males. Analysis of covariance( ANCOVA) showed that adult male head length( P0.01),head height,( P 0. 01),tail length( P 0. 01),and hind-limb length( P0.01) were significantly larger than those of the females. All the morphological traits measured showed a positive correlation with SVL. Furthermore,the growth rates of tail length( P0.05),hind-limb length( P0.05) and head height( P0.05) in males were much faster than in females. Female lizards' clutch size,clutch mass,and individual egg mass were not closely related to SVL. Our findings stand in opposition to the fecundity advantage hypothesis and support the sexual selection hypothesis as the underlying mechanisms of sexual dimorphism in P. helioscopus.