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Melanism, body condition and elevational distribution in the asp viper

Authors


  • Dedication

    We dedicate this paper to our highly esteemed co-author Jean-Claude Monney who passed away in December 2012. For this reason, we express our deep thanks for his collaboration on the ecology and evolution of the asp viper that began many years ago. We will never forget him.

  • Editor: Mark-Oliver Rödel

Correspondence

Sylvain Dubey, Department of Ecology and Evolution, Biophore Bld, University of Lausanne, 1015 Lausanne, Switzerland. Tel: +4121 692 4204; Fax: +4121 692 4165

Email: sylvain.dubey@unil.ch

Abstract

Alternative morphotypes can confer important selective advantages in different habitats, whereas they can be penalized in other circumstances. In ectotherms, such as reptiles, the body colour can have direct effects on numerous aspects of their existence, such as thermoregulation or prey–predator interactions. Darker melanic individuals show lower skin reflectance and consequently heat up more rapidly and maintain optimal body temperatures more easily than lighter coloured individuals. As a consequence, melanistic individuals of diurnal species in cool areas may exhibit higher body condition, growth rate, survival and fecundity than lighter coloured individuals. Such advantages of dark coloration may be counterbalanced by a lower crypsis to predators and a decreased foraging efficiency. We investigated, in two montane populations of asp vipers Vipera aspis, the relationship between (1) colour polymorphism and body condition and length and (2) the coloration of individuals and their elevational distribution. We showed significant relationships between (1) the coloration, body condition and sex of individuals; (2) sexes and reproductive state and morph frequency; and (3) colour morphs that were distributed following an elevational gradient. Hence, colour polymorphism plays an important role in the ecology and evolution of the asp viper and is maintained through differential selective pressures.

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