Patterns of morphological variation in the skull and cephalic scales of the lacertid lizard Algyroides nigropunctatus

Abstract

We applied a geometric morphometrics approach to examine sexual size and shape dimorphisms (SSD and SShD) in dorsal and ventral skull portions and cephalic scales (pileus) in the lacertid lizard Algyroides nigropunctatus. We found significant sexual dimorphism in all three structures that are mostly attributable to allometry. Males and females share allometric trajectories for the pileus and dorsal portion of the skull, i.e. the significant differences in shape between sexes are due to differences in size. Regardless of sex, allometric shape differences between small and large individuals show negative allometry in the anterior parts and more pronounced positive allometry of the parietal region in the dorsal skull and pileus. We observed a marginally significant divergence in sex-specific allometric trajectories of the ventral skull. The similar patterns of covariation between the ventral skull and the dorsal skull portion and pileus indicate close relationships between the skull bones and cephalic scales. The stronger covariation between the ventral and dorsal skull portion in males compared to females raises the question whether sexual dimorphism in the structure of morphological variation of the lizard skull exists.