Mathematics, Department of



A DISSERTATION Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfilment of Requirements For the Degree of Doctor of Philosophy, Major: Mathematics. Under the Supervision of Professor J. David Logan.
Lincoln, Nebraska: August, 2009
Copyright (c) 2009 Amy L. Parrott


Climate change and its effects on ecosystems is a major concern. For certain animal species, especially those that exhibit what is known as temperature-dependent sex determination (TSD), temperature variations pose a possibly serious threat (Valenzuela and Lance, 2004). In these species, temperature, and not chromosomes, determines the sex of the animal (Valenzuela and Lance, 2004). It is conceivable therefore, that if the temperature changes to favor only one sex, then dire consequences for their populations could occur. In this dissertation, we examine possible effects that climate change may have upon Painted Turtles (Chrysemys picta), a species with TSD. We investigate the magnitude and type of change required to have an adverse effect upon its population. We look at both the effects caused by an increase in average temperature and an increase in daily temperature variance. To examine these effects, we develop a computational model that connects daily ambient air temperature and solar radiation readings to the sex of the turtles in the nests and to the male/female population structure. We show that an increase in temperature or variance may cause a decline in the population, but an increase in both temperature and variance produces the greatest decline.