UC Santa Cruz

As the climate changes at an unprecedented rate, rising temperatures will have complicated consequences for organisms. Ectotherms are particularly vulnerable because rely directly on environmental temperatures to regulate their body temperatures and perform necessary functions. While extinction risk for reptiles is well studied, amphibian present a more complex system due to their life histories and their fundamental tradeoff between maintaining activity at higher temperatures versus increased rate of water loss. To understand the climate change extinction risk of amphibians, I must first understand how they respond to current and predicted future environmental conditions. To accomplish this, I first investigate how canopy density and microclimates affect environmental conditions and those cascading effects on anuran thermal physiology in Chapter 1. I used agar frog models to estimate the thermal and hydric capacities of frogs and found that many environmental variables impact frog operative temperature and water loss rates. My results suggest that, with access to diversity of microhabitats, decreasing canopy coverage provides a larger range of thermal conditions without increasing the risk of water loss for frogs. In Chapter 2, to understand the long-term acclimation potential of these animals, I examine the within and inter-generation acclimation potential of maternal, incubation, and late rearing temperature on offspring thermal physiology. My results demonstrate thermal inter- and within-generation plasticity in amphibians and show that larvae can quickly increase thermal preference and receive a major buffer to climate change. In Chapter 3, I test for outbreeding depression between two genetically distinct populations using an admixture propagation design. I found no evidence for outbreeding depression between pure line and genetic crosses. This suggests that admixture propagation is a safe method for genetic restoration and human facilitated gene flow could be used to break extinction vortexes. The results of this dissertation provide a picture of amphibians’ response to the environment, within and between generations, and at the population level. I unite all my chapters to understand the large-scale physiological patterns of amphibians facing climate change, clarify the extinction risks for these animals, and show how I can use this information in conservation projects.