The ecology and genetics of the eastern hellbender Cryptobranchus alleganiensis alleganiensis

Shem D Unger, Purdue University

Abstract

North America's giant salamander, the eastern hellbender (Cryptobranchus alleganiensis alleganiensis) is a long-lived, obligately aquatic salamander. Thus, it is a model species for investigating the genetic architecture of lotic systems. However, many populations have experienced precipitous declines and are at risk for loss of genetic diversity and increased extinction. As a result, there is a need to assess population structure and genetic diversity across the riverscape to inform management efforts. My dissertation focuses on using molecular methods and population modeling to examine the conservation biology of this cryptic species. In chapter one, I assessed the genetic structure at the range-wide and landscape or drainage level (across stream hierarchical networks of basins, sub-basins, and stream reaches). I found relatively high levels of genetic diversity range-wide, indicating high quality genetic stock for conservation efforts. Across the geographic distribution, I found two genetically differentiated groups at the range-wide scale: 1) the Ohio River drainage and 2) the Tennessee River drainage. At the drainage scale, I found most of the genetic variation partitioned within streams. I also found a strong pattern of isolation by distance at the drainage scale. In chapter two, I used molecular markers as genetic tags to assess the retention of Passive Integrated Transponder tags for eastern hellbenders within the Blue River. This provided a method for validating estimates of population size based on previous mark-recapture studies for Indiana's sole remaining population of eastern hellbenders. Lastly, in chapter three, I developed a stage-structured life-history model for the Blue River to assess the efficacy of management strategies on population growth and long-term population viability. I found a high probability of complete extirpation unless management practices are implemented to ensure adult presence and increase early life-stage survival. Several management actions are recommended to stabilize population projections, including initiating a head-starting program and conducting female-biased translocations to facilitate population growth. When taken together, this research provides a framework to inform wildlife management strategies and further our understanding of the conservation genetics and population dynamics of this cryptic salamander species.

Degree

Ph.D.

Advisors

Williams, Purdue University.

Subject Area

Wildlife Conservation|Ecology|Genetics

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