Exploring the Thermal Physiology Evolution Across Mountain Slopes

Abstract

I investigated whether critical thermal limits to low and high temperatures exhibit patterns of thermal tolerance specialization across altitudes, both between and within species, in the complex terrain of the Neotropical mountains. In these mountains, species have found different ways to adapt and diversify to their various elevational and climatic gradients (Chapter 2). I used climatic and distribution data to assess patterns and test for changes in the evolution rates of highland specialization across the entire anole phylogeny. Few animal groups have been able to adapt and thrive in several different mountain ranges (Chapter 3). I tested whether those biogeographical shifts from low elevation to high elevation have led to an increase in diversification and speciation rates (Chapter 4). Finally, I tested whether water loss is influenced more by the intrinsic physiology of the lizards or by the climatic niche they inhabit. I also investigated to what extent these two factors affect water loss in lizards (Chapter 5). I found that understanding the evolution of highland specialization and climatic niche evolution is particularly complex. Different clades have converged in their critical thermal limits, where the critical thermal minimum and maximum decrease as elevation increases (Chapter 2). This convergence suggests that high-elevation environments exert strong selective pressures that shape the thermal tolerances of species. Additionally, cold adaptation has evolved several times in similar ways when analyzed within an elevational and cold temperature framework (Chapter 3). This repeated pattern of adaptation highlights the predictability of evolutionary responses to similar environmental challenges. However, I observed distinct evolutionary trajectories between highland and lowland species, likely shaped by climatic heterogeneity and ecological specialization across elevation gradients (Chapter 4). Factors such as the temporal scale of analysis, the specific environmental variables considered, the phylogenetic context, and the climatic heterogeneity all play crucial roles in shaping our understanding of climatic niche evolution. Lastly, I discovered that water loss is intricately associated with climatic conditions, particularly temperature and precipitation (Chapter 5). The relationship between water loss and climate suggests that species have evolved mechanisms to cope with varying levels of humidity, precipitation and temperature. This adaptation is critical for maintaining hydration and overall physiological function in desertic regions