Female preferences for discrete and continuous male colour expression may help reinforce colour polymorphism in a desert lizard

Despite recognition that colour can vary continuously, colour expression in colour polymorphic species is usually treated as discrete. We conducted three experiments to evaluate the extent that discrete and continuous male coloration influenced female mating preferences in long-tailed brush lizards (Urosaurus graciosus). Each experiment provided females with a different social context: a dimorphic choice between a yellow and an orange male (coloration treated as discrete), and a choice between either two orange males or two yellow males (coloration treated as continuous variation). Females preferred orange males over yellow males in the first experiment, and the findings of our second experiment suggested that males with moderate orange coloration were most preferred. In contrast, females behaved randomly with respect to two yellow males. Our findings show that females in colour polymorphic species can evaluate both discrete and continuous aspects of morph coloration during mate assessment, which may help maintain their polymorphism.