Don't judge a lizard by its colour: no evidence for differential socio-sexual behaviour and space use in the colour morphs of the European common wall lizard (Podarcis muralis)

Explaining the evolutionary origin and maintenance of colour polymorphisms is a major challenge in evolutionary biology. Such polymorphisms are commonly thought to reflect the existence of alternative behavioural or life-history strategies under negative frequency-dependent selection. The European common wall lizard Podarcis muralis exhibits a striking ventral colour polymorphism that has been intensely studied and is often assumed to reflect alternative reproductive strategies, similar to the iconic "rock-paper-scissors" system described in the North American lizard Uta stansburiana. However, available studies so far have ignored central aspects in the behavioural ecology of this species that are crucial to assess the existence of alternative reproductive strategies. Here we try to fill this gap by studying the social behaviour, space use, and reproductive performance of lizards showing different colour morphs, both in a free-ranging population from the eastern Pyrenees and in ten experimental mesocosm enclosures. In the natural population, we found no differences between morphs in site-fidelity, space use or male-female spatial overlap. Likewise, colour morph was irrelevant to socio-sexual behaviour, space use, and reproductive success within experimental enclosures. Our results contradict the commonly held hypothesis that P. muralis morphs reflect alternative behavioural strategies, and suggest that we should instead turn our attention to alternative functional explanations