Award Date

12-15-2019

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Life Sciences

First Committee Member

Laurel Raftery

Second Committee Member

Allen Gibbs

Third Committee Member

Andrew Andres

Fourth Committee Member

Daniel Thompson

Fifth Committee Member

Kaushik Ghosh

Number of Pages

182

Abstract

Evolutionary outcomes are demonstrated by traits that affect an organism’s schedule of reproduction and survival. These life history traits are reflected in an organism’s physiology, development and behavior. Environmental changes, such as availability of nutritional resources, can profoundly affect evolutionary outcomes of individuals and populations. When shortages arise, there will be trade-offs in the allocation of resources, where one trait prevails at the expense of another.

In the laboratory, we can mimic conditions in nature and study the specific effects of the conditions that we re-create. In our case, over 100 generations of Drosophila melanogaster have been selected for starvation resistance. These starvation-selected flies exhibit some evolved phenotypes that impact reproduction, survival, cardiac function, lipid content, metabolic rate and development time.

One specific factor of interest to me, was the reduced fecundity, or egg laying capacity, of the starvation-selected flies. These females have been shown to have 45% lower fecundity than the fed controls, while retaining three times the amount of lipids. They also live three times longer under starvation conditions. The focus of my research was to look at population variation resulting from the starvation stress response in these flies, and the underlying developmental, cellular and physiological mechanisms that are the foundation to the evolutionary changes in these flies.

First, I wanted to confirm that some of the previous data on the flies remainedtrue after multiple generations of laboratory selection. Once I did that, I wanted to investigate whether there were any physiological changes in the adult female that related to egg laying capacity. Therefore, I took a closer look at the ovary. I found that the starvation-selected females had an altered ovarian anatomy that impacted the number of eggs they could produce.

That led me to look back in the fly lifecycle to see if I could determine where in development these changes may have occurred. I discovered cellular changes in the larval and pre-pupal ovaries that impacted ovarian development, and contributed to the

adult females’ egg laying capacity.

Then, I looked at larger sample sizes of flies (n=210 for each population) across seven days of female age in order to investigate peak egg laying capacity and changes in oogenesis between the treatment populations. These data further confirmed the conservative physiology of the starvation-selected females with respect to the allocation of resources to reproduction. These flies maintain a starvation-resistant trait through frugal allocation of energy to reproduction, which is expressed across generations of flies and maintains the survival of the population.

Disciplines

Biology | Ecology and Evolutionary Biology | Evolution | Medical Physiology | Physiology

File Format

pdf

File Size

2.1 MB

Degree Grantor

University of Nevada, Las Vegas

Language

English

Rights

IN COPYRIGHT. For more information about this rights statement, please visit http://rightsstatements.org/vocab/InC/1.0/

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