UC Santa Cruz

Climate change is predicted to severely impact species distributions and extinction risk in the coming decades. Ectotherms, such as lizards, are of particular concern due to their dependence on environmental temperatures to survive and reproduce. The predictions of extreme weather events and increases in global mean temperatures will affect the ability of these organisms to carry out important functions such as feeding or breeding. While we predict that these organisms will face challenges from climate change, examining whether they show evidence of coping with these changes is critical for determining extinction risk and making conservation decisions. In this dissertation, I use treatments of 3-hour (short), 6-hour (mid/control), and 9-hour (long) access to basking heat to investigate how different climate extremes, predicted to increase and worsen under climate change, would impact various aspects of pregnant viviparous European common lizards (Zootoca vivipara). The 3-hour treatments reflect an unusually long series of cool days limiting thermoregulation, 6-hours reflects the “normal” period of contemporary climate and 9-hours reflects periods of long-duration heat spells.

In Chapter 1, I look at the flexibility of females to modify their behavior to different basking treatments and how intraspecific variation between populations plays a role. My results demonstrate these lizards exhibit plasticity in basking behavior in response to varying thermal opportunity. However, the magnitude to which they modify their behavior is significantly tempered by environmental characteristics of their population of origin. In Chapter 2, I investigate how basking treatments influence gestation and offspring phenotype, as the offspring life history stage is one of great importance. We found that offspring phenotype was significantly affected by mother basking treatments with local population differences and sex-dependent outcomes on size and viability in juveniles. My findings indicate that cooler and warmer temperatures have different effects on progeny phenotype and may have cascading impacts under climate change in the next generation. In Chapter 3, I examine how parasite load varies between populations and whether basking treatments influence a lizard’s ability to fight infection. The basking treatments influenced changes in parasite load in three of the five populations, where we observed a relatively small increase in parasite abundance in lizards in the short and mid/control basking treatment compared to the long treatment. This difference between populations suggests a context-dependent impact of basking opportunities on the capability of lizards to clear parasite infections, under the warm environment treatment (9-h) and provides further evidence that ectothermic host-blood parasite relationships are likely to be impacted by future and contemporary climate change.

The results of this dissertation ultimately highlight the complex impacts climate change can have on these organisms and will hopefully encourage further research while raising awareness of this pressing issue.