Colour polymorphism, alternative breeding strategies and assortative mating in common wall lizard (Podarcis muralis): effects on fitness traits and genetic divergence among morphs

摘要: Colour polymorphism is widespread in animals, but mechanisms underlying morph evolution and maintenance are not completely resolved. In reptiles, colour polymorphism is often genetically based and associated with alternative behavioural strategies in both sexes. When morphs underlie alternative reproductive strategies, individuals showing alternative colourations usually differ not only in morphology, but also in immunological, physiological and behavioural traits as a result of correlational selection which favour the evolution of co-adapted gene complexes in a sexually selected runaway process. Noteworthy, if non-random mating such as positive assortative mating and selection against hybrids occur in the population, further genetic differentiation among morphs could be promoted, eventually leading to complete isolation and sympatric speciation. By contrast, disassortative mating enhance gene flow among morphs and intraspecific polymorphism maintenance. The common wall lizard (Podarcis muralis) is a small European lacertid showing three ventral colour morphs (white, yellow and red) and two intermediate (ie dichromatic) phenotypes (yellow-red, white-red) in both sexes and within the same population. Colourations are expressed at the time of sexual maturity and do not change during individual life, strongly suggesting that morphs could be genetically determined. To date, it has been shown that colour morphs differ in immunological and haematological features, leading to the hypothesis that they could have evolved alternative strategies to achieve different selective physiological optima dealing with different selective pressures …