Developmental responses to pond desiccation in tadpoles of the British anuran amphibians (Bufo bufo, B-calamita and Rana temporaria)

Tadpole development was compared in three amphibian species (Bufo calamita, B. bufo and Rana temporaria) that suffer different risks of pond desiccation in nature. Using a replicated pond system, development was monitored in desiccating and non-desiccating ponds, and in vertical-sided and gently shelving ('shoreline') ponds. In desiccating ponds, tadpoles suffered from crowding effects and metamorphosed at a smaller size, but development was not accelerated in response to desiccation in any of the three species. Desiccating ponds had higher maximum temperatures but also lower minimum temperatures, which may explain the lack of ally difference in development time between desiccating and non-desiccating ponds. Although shoreline ponds were slightly warmer than vertical-sided ponds, development under these conditions was also consistent with a crowding, rather than a temperature, effect. In shoreline ponds, metamorphosis generally took longer, was less synchronized between individuals, and resulted in a smaller size at metamorphosis, compared to development in vertical-sided ponds. The lack of species-by-desiccation interactions indicated that there were no differences between the three species in developmental plasticity. Developmental constraints may place a limit on the degree of plasticity that can evolve in a species such as B, calamita, which breeds only in ephemeral ponds with a variable hydroperiod. Alternatively, low genetic variability within British populations of B. calamita may have cont;trained the evolution of adaptive plasticity in this species.