Colour variation in female common lizards: why we should speak of morphs, a reply to Cote et al.


Elodie Vercken, Université Paris-Sud XI, Laboratoire Ecologie, Systématique, Evolution, UMR 8079, bat. 360, 91405 Orsay, France.
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Female common lizards display variation in their ventral colour, ranging from pale yellow to bright orange. In a previous study, we proposed a discrete classification of this variation into three colour classes: yellow, orange and mixed. However, a recent study reported on continuity of reflectance spectra and plastic change in spectrum components in female common lizards, which made the authors question the validity of a discrete classification of colour patterns in this species. Here, we discuss the relevance of discrete, eye-based colour classification for understanding the ecological processes that shape the social structure of common lizard female populations. First, as the mixed colour class is characterized by heterogeneous distribution of colour, we explain that it cannot be reliably described by localized spectrophotometer measurements. On the contrary, the classification of colour into three discrete classes is consistent with the description of three alternative strategies in female common lizards. Then, although we support the ecological importance of colour plasticity in this species, we refute the hypothesis of a condition-dependent signal, which is not supported by experimental data. At last, we explain that colour plasticity, and in particular hormone-mediated plasticity is compatible with genetic inheritance of colour and the evolution of alternative strategies. Indeed, the genetic background and the environment, especially the social environment, are expected to interact adaptively to modulate the expression of colour signals and alternative strategies.