Frequency-dependent reproductive success in female common lizards: a real-life hawk–dove–bully game?

Abstract

Alternative strategies are characterised by context-dependent fitness payoffs, which means that their fitness depends on the frequency and the nature of their interactions with one or more strategies. The analysis of the variation of the fitness of each strategy in different social environments can elucidate the evolutionary dynamics played by the strategies. In the common lizard, three female colour types (yellow, orange and mixed) are associated with alternative reaction norms in reproduction and social behaviour that signal alternative strategies. To clarify the nature of colour-specific interactions and their influence on female fitness, we analysed the response of female reproductive success to an experimental manipulation of colour frequencies in natural populations. We found that juvenile body condition at birth for all colour types was negatively affected by the local frequency of yellow females. In addition, we found that mixed females had higher clutch hatching success in the populations where orange females were frequent. These results prove that female reproduction is sensitive to the social environment, and are consistent with a scenario of a hawk–dove–bully game, in which yellow females are aggressive hawks, orange females non-aggressive doves, and mixed females have a context-dependent bully strategy. In this system, the plastic bully strategy would confer a reproductive advantage to putative heterozygotes in some social environments, which could allow the maintenance of the system through context-dependent overdominance effects.