Advisory Committee Chair
Daniel A Warner
Advisory Committee Members
Date of Award
Degree Name by School
Master of Science (MS) College of Arts and Sciences
The conditions that embryos experience during development have substantial effects on offspring phenotypes and fitness. Although plastic responses to developmental environments are widespread, whether they are adaptive is unknown in most cases. Developmental plasticity is often thought to be adaptive in heterogeneous environments, but it can also enhance fitness when environments experienced by embryos provide cues for the conditions they will eventually experience later in life. Under the latter scenario, early embryonic conditions could program an individual’s physiology to appropriately deal with predictable future conditions. This hypothesis has received support in the ecological and medical literature on diverse organisms. However, virtually all experimental tests of this hypothesis are performed in laboratory settings and do not appropriately simulate natural environmental variation. Hydric conditions of the egg incubation substrate are important for embryonic development of many reptiles. Moreover, different types of substrates have different moisture holding capacities that affect offspring development. In this study, eggs of the brown anole lizard (Anolis sagrei) were incubated under four conditions that mimic natural variation in substrate type and moisture. Our study site consists of two islands characterized by broken shell/sand substrate and little vegetation (i.e., open, arid, dry), and two forested islands with dark organic soil substrate (i.e., shaded, cool, wet). To quantify the phenotypic effects of this environmental variation, eggs were incubated in a 2x2 factorial design using both substrate types at two water potentials (-30 and -600 kPa). After hatching, morphology and desiccation tolerance of the offspring was measured, and followed by release of all individuals across the four islands for mark-recapture to quantify their survival in the two island environments. The incubation treatments greatly influenced embryo development, hatchling morphology and desiccation physiology. Eggs experiencing wet conditions rapidly increased in mass and incubated for a longer period than those in dry conditions, particularly in the broken shell/sand substrate. Furthermore, wet incubation resulted in larger hatchlings with reduced desiccation tolerance. Recapture data demonstrate that offspring survival is high on open, arid, dry islands, but only for individuals that experienced dry conditions as embryos. These results suggest that harsh developmental conditions prepare offspring for harsh post-hatching environments, providing evidence that plastic responses of embryos to the surrounding moisture environment is adaptive in nature.
Cates, Corey Dale, "The Adaptive Significance of Phenotypic Plasticity in the Wild: An Experimental Test Using the Brown Anole Lizard (Anolis sagrei)" (2015). All ETDs from UAB. 1341.