Quantitative and structural variation in skin secreted toxins across populations of the frog Bombina pachypus (Anura: Bombinatoridae)

Abstract. Skin secretions of amphibians have been intensively studied because of their pharmacological properties and their potential use in clinical applications. In many species, the substance secreted contains different peptide families, which are stored in skin granular glands and released when the animal is stressed, for example when under attack by a predator. Although the skin secretion of many species has been molecularly characterised, any insight in natural variation within species and/or populations is absent. Understanding what influences natural secretion variation could improve the knowledge in evolutionary processes and forces that drive their adaptive evolution. Here, skin secretion variation is examined in eight populations of Bombina pachypus, broadly covering the species’ distribution range. Variation in poison production, as well as in the concentration of the key toxin bradykinin, are examined in light of intrinsic (morphological) and extrinsic (environmental) variables. Latitude, altitude and sexes turn out to be variables that mostly influence poison production, with an increase in poison quantity towards the south and towards higher altitudes. Potential explanations for higher poison production in males are further discussed.