Bigger or faster? Spring and summer tadpole cohorts use different life‐history strategies

Abstract

Temporal variation in environmental conditions is a situation faced by prolonged breeders. Yet, few experimental studies provide evidence that such variation may lead to temporal divergence in life-history strategy. The breeding season of a prolonged breeder, the Indian rice frog Fejervarya limnocharis, is interrupted by a mid-summer drainage between the two rice crops, which separates the breeding population into spring and summer cohorts. We used a common garden experiment to test whether tadpoles of the two cohorts have evolved different metamorphic strategies to cope with different environmental temperatures. In a temperature (low and high) by cohort (spring and summer) factorial experiment, we found both spring and summer tadpoles had greater body growth rates, less weight loss before metamorphosis, and thus potentially higher fitness, when raised under their respective field temperatures. The spring tadpoles responded to low temperature with higher body weight at metamorphosis, while the summer tadpoles did not have such a response. On the other hand, while both spring and summer tadpoles responded to high temperature with accelerated developmental rates, summer tadpoles grew significantly faster than the spring ones. In conclusion, the study shows that spring and summer cohorts of Indian rice frog F. limnocharis use different life-history strategies to obtain higher fitness in their respective thermal environments.