Abstract
BackgroundGlobal warming has been frequently demonstrated to increase growth rate in larval amphibians that have considerable phenotypic plasticity; this may lead to an increase in larval survival because large larvae are less likely to be captured by gape-limited predators. This study is to test whether warming could improve tadpole growth and thereby enhance the tadpole survival in plateau frog Rana kukunoris.MethodologyWe conducted an experiment involving growing tadpoles under two contrasting temperatures, i.e. ambient temperature vs. warming by 3.8°C, with and without their major predators – the gape-limited predaceous diving beetles Agabus sp. in eastern Tibetan Plateau, in a factorial arrangement. We recorded the survival and measured body fresh weight and morphological characteristics of the tadpoles.Principal FindingsWarming significantly increased body fresh weight in the presence of predators after three weeks of treatments. However, the predators imposed significant and similar effects on the survival of tadpoles under both ambient and elevated temperatures, with the effects mostly occurring in the first three weeks of the experiment. Changes in the body form, i.e. the greater whole length at a given fresh weight and the longer tail at a given body length, could have acted as mechanisms of defense and escape for the tadpoles.Conclusions/SignificanceWarming did not increase tadpole survival with or without presence of predators. Moreover, an increased growth rate (due to warming in the presence of predators) was not a major factor contributing to the tadpole survival. We postulate that even if warming increases the tadpole growth rate in the plateau frog, it does not necessarily improve their survival in the presence of gape-limited predators.
Highlights
Global average surface temperature had increased by 0.85uC from 1880 to 2012 [1] and is predicted to further rise by 2 to 6uC at the end of the 21st century [2]
Tadpoles may employ various defensive mechanisms against predators, including growing long tails to increase swimming ability and strong muscles to physically fend off predators [12,13], advancing the timing of metamorphosis to leave aquatic habitats [7], and increasing growth rate to become too large for predators [5,14,15]
The warming effect was generally nonsignificant on tadpole survival, and no significant difference was observed between the two predator-absence treatments and between the two predator-presence treatments over the duration of the experiment (Fig. 1A, Appendix S3)
Summary
Global average surface temperature had increased by 0.85uC from 1880 to 2012 [1] and is predicted to further rise by 2 to 6uC at the end of the 21st century [2]. Global warming may significantly change the behavior, growth rate, and reproductive phenology of a species, and further affect its relationship with other interacting species. The declines and even extinction of some amphibian species world-wide are frequently attributed to climate change in recent decades [6], few studies have explicitly addressed the warming effect on predation-prey interactions involving amphibians and other ectothermic animals (but see [5]). If warming causes a slight change in the defensive traits or activities in either one of the players, the tadpole-predator interaction and associated tadpole survival may be significantly altered. Global warming has been frequently demonstrated to increase growth rate in larval amphibians that have considerable phenotypic plasticity; this may lead to an increase in larval survival because large larvae are less likely to be captured by gape-limited predators. This study is to test whether warming could improve tadpole growth and thereby enhance the tadpole survival in plateau frog Rana kukunoris
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