UNDERSTANDING THE PHENOTYPE: A STUDY ON HOW THE INCUBATION ENVIRONMENT INFLUENCES EMBRYO GROWTH, SEX, AND SEX RATIOS IN TURTLES WITH TEMPERATURE DEPENDENT SEX DETERMINATION

Currently, one of the most critical research priorities in wildlife science is to understand, describe, and predict how the unprecedented rate of climate change will impact organisms and ecosystems. This is particularly essential for thermally sensitive organisms that are already imperiled, such as turtles.
For all known turtle species, the nest incubation environment plays a critical role in many developmental processes which can directly influence a number of phenotypic traits, such as body size, mass, locomotor performance, behavior and even sex. Most chelonians (and all extant marine turtles) possess a mechanism known as temperature dependent sex determination (TSD), whereby gonads differentiate into ovaries or testes depending on the incubation temperature of the eggs during a critical period of embryonic development. The rapid rate of climate change highlights the need for a clear understanding of how potential changes in the nest environment will affect turtle development and hatchling phenotype. However, it is poorly understood how different environmental factors interact with the embryo’s own genetic program to produce a specific phenotype. My thesis aims to (i) provide a better understanding of the complex relationship between the developing embryo and the nest environment and its effect on hatchling phenotype, and (ii) offer a solution to the difficulties associated with identifying primary sex ratios in turtle species with TSD.