Abstract
Colour polymorphism may be accompanied by alternative expressions of phenotypic traits that are directly or indirectly related to fitness, and selection forces may act on the traits separately or concurrently. In polymorphic species, natural selection may act through frequency- or density-dependent mechanisms and maintain polymorphism through interactions among morphs. We used an integrative approach to examine functionally relevant and interrelated life history traits in the context of colour polymorphism in the European wall lizard (Podarcis muralis). Body, head and limb morphology, bite and locomotor performance, and physiology, particularly metabolic and antioxidant capacity, were analysed in the three pure colour morphs (yellow, orange, white) and the two mosaic morphs (yellow-orange and white-orange). Morphological differences between morphs were present but subtle and consisted mainly of variations in head length. Head size and bite force were strongly associated between and within morphs. Limb and boot morphology and locomotor performance (sprinting and climbing) were variably associated among morphs. Finally, variation in biochemical indicators of cellular metabolism and antioxidant capacity appeared to be largely independent of morphology and performance. The results provide evidence for existing and non-existing relationships between colour and morphology, performance, and physiology that could have short- and long-term effects on selection.
Highlights
Captured males of three pure colour morphs and two mosaic colour morphs did not differ in body and head size (SVL and Head size (HS)) or limb length (FLL and hind limb length (HLL)) (Tables 1 and 2)
Despite the robust sample size and multivariate analysis, we found only a weak to no polymorphic pattern in morphology, performance, and physiology between the three pure colour morphs and the two mosaic morphs in Podarcis muralis population from the southern Pyrenees
Morphological differences between morphs exist but are subtle and consist mainly of variations in head length, with yellow and yellow-orange lizards having smaller heads compared to the other colour morphs
Summary
Colour is one of the most variable and noticeable phenotypic traits in the natural world. In non-avian reptiles, including lizards, pigments and structures responsible for colour production are contained in specialized cells known as dermal chromatophores [1,2,3]. The variation in chromatophore content and the combination between the different chromatophore types generates the high variability of colours and patterns described in this animal group. Diurnal lizards possess a complex colour vision system composed by four different cone types, as well as double cones, allowing the discrimination of a large range of colours [4]. Most colour patches of lizards are often interpreted as visual signals, especially those showing a conspicuous appearance to conspecifics (e.g., [5,6,7,8])
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