Honors College Theses

Publication Date



Biology (B.S.B.)

Document Type and Release Option

Thesis (open access)

Faculty Mentor

Dr. Heather Joesting


Phenotypic plasticity is the ability of an organism to change morphology and/or physiology in response to changes in the environment. Hydrocotyle bonariensis is a coastal perennial herb found in both coastal sand dunes and inland coastal plain habitats in Georgia. The purpose of this study was to determine if there were differences in leaf morphology for populations of H. bonariensis in coastal sand dune and inland coastal plain habitats. Leaf morphology and microenvironmental variables were compared between H. bonariensis populations at Tybee Island (TI), GA, representing the coastal sand dune habitat, and Georgia Southern University Armstrong Campus (GSU) in Savannah, GA, representing the inland coastal plain habitat. According to results, populations at TI experienced significantly greater incident sunlight, air temperatures, and soil temperatures compared to GSU populations, and TI soil contained a greater percentage of sand particles, indicating lower water-holding capacity, and lower organic matter and nutrients. Furthermore, H. bonariensis leaves from TI had significantly greater leaf fresh weight, dry weight, water weight, thickness, and chlorophyll content than leaves from GSU. Leaf morphology results suggest that leaves from TI generally have a structure that facilitates relatively greater water-retention and chlorophyll content, likely influenced by the low water-holding capacity of the sandy soil and high incident sunlight characteristic of the sand dune habitat. These results will provide greater insight into the role of phenotypic plasticity in the ability of plants to occupy environmentally different habitats.