Phenotypic Plasticity in Larval Development of Six Amphibian Species in Stressful Natural Environments

Phenotypic plasticity is known as the capacity to change in response to different environmental conditions, and if these changes imply reversible transformations, it is known as phenotypic flexibility. This plasticity includes changes in behavior, physiology, morphology, growth, life history, and demography, and can be expressed either within the lifespan of a single individual or across generations. Plasticity in amphibian species, which breed in extreme conditions at the southern frontier of their distributions, allows an individual to prolong the larval period and maximize its size at metamorphosis when conditions are favorable. Plasticity may allow tadpoles to avoid mortality in a desiccating habitat by accelerating metamorphosis and reducing their size at metamorphosis. This study examined 6 species of amphibian larvae over several years that grew and completed metamorphosis at 14 ephemeral and permanent breeding sites in a Mediterranean climate. The aim of the current study was to test the ability of these 6 species to undergo phenotypic changes in larval size and the course of metamorphosis relative to time, in response to various water-quality parameters. Of the 6 species tested, the salamander was the only species that occupied all types of breeding sites that were sampled and showed significant differences in growth rates and sizes of tadpoles during metamorphosis by comparison between individuals from different pools. Five other species mainly inhabited ephemeral pools. There was no significant difference in the timing of metamorphosis, but for some species there was a significant difference in the final size of the tadpoles. In 2 poorly fed, completely dark, and very shallow breeding sites, we found Salamandra infraimmaculata larvae for longer periods and with a smaller size at metamorphosis.