Throat colour polymorphism in relation to sex and body size of the Litter skink, Lankascincus fallax

Colour polymorphism is a pervasive phenomenon in both animal and plant kingdoms and understanding its evolution and maintenance is of great interest. Among the lizards of Sri Lanka, the endemic skink Lankascincus fallax shows throat colour polymorphism in which, the underlying basis is not clearly known. In this study, we examined the relationship of the three different throat colour morphs observed in this species with the sex, body size and the geographic location of L. fallax. Live skinks were sampled from two locations in Sri Lanka and sex and the throat colour was categorized visually and the snout to vent length (SVL) was measured. Tail tips of some selected individuals from the two locations were taken and a fragment of the 12S rRNA gene was sequenced in representative individuals having the different throat colour morphs. Pairwise genetic distance of the three colour morphs ranged between 0.4-0.5% confirming that the three colour morphs were the same species. Three colour morphs (red, black and white) were observed in males in both locations, while only the white morph was observed in females, suggesting that the throat color polymorphism was confined to males. There was a significant difference between the mean SVL of males with red and black throat colours (39.35 mm) and males with white throat colours (30.31 mm). Thus, the study suggests that the throat colour in these skinks is highly associated with sex and the body size in males. The study further suggests that L. fallax is sexually dichromatic and that the males show throat colour polymorphism. However, future studies are necessary to understand the underlying drivers for the presence and maintenance of sexual dichromatism and throat colour polymorphism in L. fallax.