Experimental and molecular evidence that body size and ventral colour interact to influence male reproductive success in a lizard

This study aimed to first investigate the relationship between male ventral colour, body size and ectoparasite load, and then test, using an enclosure experiment, how body size and ventral colour influence male reproductive success in a non-territorial lizard. Individuals of the sexually dimorphic Australian skink, Pseudemoia entrecasteauxii, were sampled in the field and male body size and ventral coloration were recorded. The frequency of orange and white ventral colour appeared bimodal; males either had orange or white ventral colour. While larger males were more likely to have orange ventral colour, there was considerable variation and small males with orange ventral colour and large males with white ventral colour were common. The number of mites each male had was positively correlated with snout vent length, weight and head depth corrected for body size and was greater for males with orange ventral colour. Mating trials in outdoor enclosures were used to investigate the separate and combined effects of male ventral colour, body size and male behavior on reproductive success. Behavioural observations revealed that males with orange ventral colour were dominant over males with white ventral colour and, contrary to expectations, male body size was not related to dominance. A total of 32 neonates were genotyped along with their mothers and potential fathers using three polymorphic DNA loci. Large males with orange ventral colour fathered the most neonates. These findings suggest that although males with orange ventral colour were dominant, both body size and ventral colour influenced male reproductive success.