Male mate choice based on female coloration in a lizard: the role of a juvenile trait

In many animals, females choose males for mating in relation to their conspicuous coloration, but males can also select females by display traits. In a lizard species in which females show red tail coloration during the mating season, tail color was experimentally manipulated and males preferred red versus white adult females for courtship. Red coloration makes females more sexually attractive in this lizard species, possibly because it indicates sexual maturity and a pre-ovulatory reproductive status. Abstract Female mate choice for male display traits is widely observed across animal taxa and is a well-established mechanism of evolution. However, males are increasingly seen to exhibit mate choice for female display traits, even in species with traditional sex roles, although this continues to be an understudied aspect of sexual selection. We evaluated the role of female coloration on male mate choice decisions in the spiny-footed lizard (Acanthodactylus erythrurus), a species in which adult females show red coloration as a retained juvenile trait. Although both sexes show red tails as juveniles and subadults, only females maintain red colored tails when becoming adult; moreover, this coloration is only present at the beginning of female adulthood and becomes white after ovulation, suggesting a mating-related function. Male courtship preferences were investigated through an experimental approach, where they were offered pairs of females that differed in size (adult/subadult) and tail coloration (red/white). Male lizards preferred adult females using both visual and chemical cues and, when adult female coloration could be chosen, they preferred red females. These results suggest that red coloration is a sexual signal involved in male mate selection. We hypothesize that red coloration in adult females might indicate sexual maturity and a pre-ovulatory reproductive status. Being a juvenile trait retained until the beginning of adulthood, we also suggest that it might indicate reduced risk of sperm competition. This study highlights the role of a juvenile trait for sexual selection and adds to the understanding of the evolution of male mate choice.