Oxidative cost of interspecific hybridization: a case study of two Triturus species and their hybrids

Oxidative stress has most recently been suggested as one of possible mechanisms responsible for reduced fitness of hybrids. To explore possible oxidative cost of hybridization, we examined antioxidant defense system parameters (superoxide dismutase, catalase, glutathione peroxidase, glutathione s-transferase, glutathione reductase, glutathione, SH groups), their interconnectedness (index of integration), and levels of oxidative damage (concentrations of lipid peroxides-TBARS) in lab-reared newt species, and , and their hybrid. Our results showed that parental species differed in antioxidant defense system parameters, but not in the levels of integration of the whole system and oxidative damage. Individuals of had higher activities of superoxide dismutase, glutathione s-transferase and concentrations of glutathione. Hybrid individuals of crested newts displayed higher levels of the antioxidant defense system (higher superoxide dismutase, catalase, glutathione peroxidase activities and concentrations of SH groups), and a lower overall correlation of antioxidant system (lower index of integration) in comparison to both parental species, suggesting that they may possess a less efficient antioxidant defense system and a higher investment in maintaining oxidative balance. The higher investment in the antioxidant system could divert limited resources away from other functions and affect further hybrid fitness. The presented findings contribute to a better understanding of the antioxidant defense system of crested newts and their interspecies differences, and support the hypothesis that oxidative stress is one of the costs of interspecific hybridization.