Plasticity of metamorphic traits in a high-altitude toad: interactive effects of food level and temperature

Abstract

In organisms with complex life cycles, such as amphibians, morphological variation itself is strongly influenced by environmental factors and maternal effects. Although temperature and food level exert a strong influence on larval growth and development, little is known about the interacting effects of these factors on age and size at metamorphosis. In this study, plasticity in growth rates, larval mass, larval period, and body size at metamorphosis were experimentally examined for a high-altitude toad (Bufo minshanicus) under different combinations of temperature and food level. Larval period and mass at metamorphosis were sensitive to food level, and varied with temperature. At high food level, tadpoles reared at 29.8°C had shorter larval period lengths and larger mass at metamorphosis than those reared at 25.8 and 22.6°C, but not between 25.8 and 22.6°C. Interestingly, tadpoles at 29.8°C that were offered with a higher level of food supply achieved a larger size than those with a lower level of food supply; however, food supply did not affect body mass at the two lower temperature settings. Thus, the effects of food level were dependent on water temperature. Although there was high mortality at 29.8°C, surviving tadpoles have been much stronger to achieve faster growth and reach a larger mass at metamorphosis, which were positively correlated with juvenile survival and adult fecundity. Thus, under varied environmental conditions, we could say that there is more plasticity in development and growth of larvae in high altitude populations than in the same species or other species from low altitude populations.