Date of Award
2026
Document Type
Dissertation
Degree Name
Biological Sciences (Ph.D.)
Department
Biological Sciences
First Advisor
Juan C Santos
Second Advisor
Javier F Juarez
Third Advisor
Robert Kozol
Abstract
Adaptation to ecological pressures often shapes survival, reproduction, and diversification across animal lineages. In this dissertation, I investigated how parental care, aposematism, thermal biology, coloration, and respiratory physiology interact to influence the evolutionary trajectories of amphibians and reptiles. First, I examined the interplay between aposematism and diversification of parental care strategies in poison frogs (Dendrobatidae) under a phylogenetic comparative approach. Second, I investigate the evolution of body temperature in dendrobatids and its evolutionary correlation with ecological, environmental, and life-history data. Additionally, I explore the role of environmental context and antipredator strategies in shaping physiological evolution under current and future climates. Third, I study the evolution of gene expression in Mantella poison frogs. Transcriptomic analyses revealed that gene expression in skin is largely constrained by stabilizing selection, with only a small subset of genes diverging among lineages. Candidate pigmentation genes correlated with coloration, with reduced melanin-pathway activity facilitating the evolution of bright orange phenotypes. These results highlight how fine-scale shifts in gene regulation underlie conspicuous color evolution while broader transcriptomic patterns remain conserved. Finally, I examined the molecular evolution of hemoglobin subunits in reptiles to test how respiratory proteins are related to environmental gradients such as altitude, temperature and productivity. Together, these studies illuminate how ecological pressures, life-history traits, and molecular mechanisms interact to shape evolutionary outcomes across ectotherms. By integrating phylogenetics, physiology, and transcriptomics, this work advances our understanding of adaptation and diversification in amphibians and reptiles.
Recommended Citation
Carvajal Castro, Juan David, "EVOLUTIONARY AND ECOLOGICAL IMPLICATIONS OF COLORATION IN POISON FROGS, WITH NOTES ON MOLECULAR EVOLUTION IN ECTOTHERMIC VERTEBRATES" (2026). Theses and Dissertations. 1043.
https://scholar.stjohns.edu/theses_dissertations/1043