Date of Award

Spring 5-2010

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Sciences

Committee Chair

Dr. Carl Qualls

Committee Chair Department

Biological Sciences

Committee Member 2

Dr. Brian R. Kreiser

Committee Member 2 Department

Biological Sciences

Committee Member 3

Dr. Jodie Jawor

Committee Member 3 Department

Biological Sciences

Committee Member 4

Dr. Robert Jones

Abstract

The role of species conservation is becoming increasingly important due to the mounting pressures from humans on habitats and populations of organisms. This is particularly evident in riverine ecosystems throughout the world where the human demand for freshwater resources is increasing, and consequently, the number of imperiled aquatic organisms is also growing. The seven chapters of this dissertation primarily focus on the Yellow-blotched Sawback, Graptemys flavimaculata, an endangered riverine turtle that is endemic to the Pascagoula River system of southeast Mississippi, USA. At the population level, we aimed to study the impacts of Hurricane Katrina on two study populations within the Pascagoula River system, while also determining likely causes of population decline related to the storm. On a larger scale, we sought to determine the current distribution and abundance of G. flavimaculata, as well as another similar species (Pascagoula Map turtle, Graptemys gibbonsi), throughout the Pascagoula River system. At the individual/population level, we wanted to better understand the basking ecology of the species by analyzing basking behavior throughout the active season. In addition, the role of human recreation on the species was studied by measuring behavioral (basking) and physiological (stress hormone levels and shell condition) responses of turtles to human activities. Lastly, we aimed to determine the level of connectivity of G. flavimaculata throughout the Pascagoula River system by measuring levels of genetic differentiation among sampled populations.

Our results indicated that Hurricane Katrina had a significant negative impact on coastal populations, whereas an upstream population was not similarly impacted. We suspect that following the hurricane, water quality was likely compromised, leading to an impact on prey items and subsequent impacts on turtle populations. Our distribution/abundance surveys found both Graptemys species in new localities, in smaller drainages than earlier studies, and generally in higher population densities than previously recorded; our coastal population, however, did not rebound in the three years following Hurricane Katrina. Our basking ecology study found that turtle basking behavior was dependent on the season, time of day, and the sex of the individual. Also, we found differences among the sexes in basking structures used, but little correlation was found with population-level basking and measured environmental temperatures. Our recreational impacts study found significant impacts of boating activities on our coastal population relative to our inland population. The former had significantly shorter individual basking durations and significantly lower population-level basking percentages, while also having poorer physiological condition as measured by shell condition. However, we found no correlation between recreational activities and baseline/corticosterone stress response measures. Further, larger/slower boats disturbed significantly higher numbers of turtles relative to smaller/faster boats. This is significant as registered boats in Jackson County, MS (county of our disturbed site) have increased 300% over the last 22 years. Results of our genetic analysis indicated that genetic differentiation was significant among almost all sampled populations with isolation by distance likely being the driving mechanism; the Escatawpa population was found to be the most genetically distinct population, with differentiation likely derived from a historical isolation from the main river populations. We hope that this research, conducted on multiple scales, will provide quality information for conservation planners/managers to preserve viable turtle populations and intact riverine habitat throughout the Pascagoula River system into the future.

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