Plasticity and resilience of ectotherms to climate change

Abstract

Climate change is one of the greatest challenges of our era, and identifying the most vulnerable populations is urgently needed to guide conservation efforts. At the heart of this challenge is temperature, the main choreographer of ectotherms’ physiological functions. Accumulating evidence points to climate change nudging temperatures dangerously close to the physiological limits of ectothermic species, compromising their distribution and survival in a warming world. This thesis explores the potential for phenotypic plasticity to buffer ectotherms from temperature extremes and develop new approaches to enhance our understanding of global macroecological patterns. In Chapter I, I use meta-analysis to explore sex-based variation in plasticity, revealing weak yet heterogeneous differences between males and females. Chapter II goes further in exploring variation in plasticity, examining the extent to which developmental temperatures impact the thermal tolerance of embryos and juveniles. My findings revealed weak plastic responses across ectotherms, with embryos emerging as potentially the most vulnerable life stage in a warming world. In Chapter III, I build a comprehensive database of the thermal tolerance of amphibians. Despite efforts to integrate multilingual evidence, this chapter highlighted major biases in sampling - most data originating from temperate regions, in contrast to the greater species richness in the tropics. Chapter IV leverages this database and integrates thermal tolerance, environmental exposure, and plasticity to assess the resilience of amphibians to global warming. This chapter also introduces a novel data imputation approach to solve geographical and taxonomical biases identified in Chapter III, ultimately revealing the considerable vulnerability of amphibians to extreme heat events at a truly global scale. Finally, Chapter V reflects on insights gained from previous chapters and proposes new horizons for comparative studies and meta-analyses. Overall, this thesis shows how comparative studies and meta-analyses can shed light on global patterns in the plasticity and resilience of ectothermic species, and how synthesizing existing data can deepen our understanding of unexplored patterns and dynamics