Date of Award

Spring 8-1-2004

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Life Sciences

First Advisor

Michael J. Angilletta

Second Advisor

Charles J. Amlaner

Third Advisor

George S. Bakken

Abstract

Geographically widespread ectotherms encounter thermal gradients that generate variation in behavior, physiology and life-history. Because rates of physiological processes are very sensitive to temperature, cold environments are thought to favor genotypes that have relatively high capacities for growth despite environmental constraints. Two different adaptive responses can occur: (1) mothers in colder environments can allocate more energy to each offspring, or (2) offspring in colder environments make more efficient use of available resources. In this study, I examined both maternal adaptations and embryonic adaptations to environmental temperature. Evidence of maternal adaptations was assessed by examining the relationship between egg size and temperature within and among five distinct populations (NJ, VA, SC, IN and FL) of the eastern fence lizard (Sceloporus undulatus) and by expanding the investigation to the Phrynosomatid family, which includes S. undulatus and its relatives. In addition to variation in egg size within the five populations of S. undulatus, the energetic content was examined to explore the adaptive and non-adaptive interpretations of the variation in egg size observed. Embryonic adaptation was examined by measuring both growth efficiency and incubation period in the same five populations of S. undulatus, to determine if individuals from cold populations grow more efficiently and hatch earlier than individuals from warm environments under similar environmental conditions. Evidence of both maternal and embryonic adaptations was found. Although there was no relationship between temperature and egg size within the Phrynosomatid family, there was among the populations of S. undulatus. Additionally, evidence of embryonic adaptation in increased rates of growth and development in individuals from northern populations (NJ, VA and IN) was found. This study demonstrates that, although the opportunities for growth might be reduced in northern environments, individuals counteract this phenomenon counteracting the pressures through both maternal and embryonic adaptations.

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