Date of Award

12-2017

Degree Type

Honors College Thesis

Department

Biological Sciences

First Advisor

Jake Schaefer, Ph.D.

Advisor Department

Biological Sciences

Abstract

Developmental plasticity refers to changes during development as a result of environmental contributions. Salinity is a varying environmental condition in freshwater and estuarine habitats that can mediate developmental plasticity in Gambusia affinis, which can increase their tolerances as an invasive species. For my study, estuarine and freshwater populations of Gambusia affinis were sampled in March of 2017 using dip nets. Both populations were then brought back to the laboratory where pregnant females were acclimated to three different salinities (0‰, 15‰, 25‰) until they gave birth. I predicted that the estuarine population of Gambusia affinis would have a greater salinity tolerance than the freshwater population of Gambusia affinis and that for both populations, the offspring reared at the highest salinity would have a greater salinity tolerance than the offspring reared at the lower salinities. Their offspring remained in their tanks where they were birthed until they reached maturity and then were acclimated back to 0‰ for two weeks to look specifically at developmental plasticity. After the two-week acclimation period, the offspring were directly transferred into 24-hour experimental trials run at 20‰, 25‰, and 30‰ and survivorship was assessed. It was determined that salinity does mediate genetic and, specifically, developmental plasticity effects. The estuarine population of Gambusia affinis does have a greater salinity tolerance than the freshwater population of Gambusia affinis and that for both populations, the offspring reared at the highest salinity had greater salinity tolerance than the offspring reared at the lower salinities. If developmental plasticity is playing a larger role than genetics in determining individual tolerances, this can increase the survivorship and increase its distribution as an invasive species to even more non-native habitats because of these nonreversible effects and adaptable tolerances.

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