Date of Award

Spring 5-13-2016

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Sciences

Committee Chair

Dr. Carl P. Qualls

Committee Chair Department

Biological Sciences

Committee Member 2

Dr. Brian R. Kreiser

Committee Member 2 Department

Biological Sciences

Committee Member 3

Dr. Micheal A. Davis

Committee Member 3 Department

Biological Sciences

Committee Member 4

Dr. Jacob F. Schaefer

Committee Member 4 Department

Biological Sciences

Committee Member 5

Dr. J. Hardin Waddle

Abstract

During the last half century, lungless salamanders (Family Plethodontidae) have been the subject of numerous studies in the fields of ecology and genetics. While most works have focused on the species-rich Eastern Highlands region, there has been a recent shift towards plethodontid assemblages within the Coastal Plain. The research presented herein applies hierarchical occupancy models and both mitochondrial and nuclear genes to address questions pertinent to the biology and conservation of plethodontids within the Gulf Coastal Plain. The results of a multi-species Bayesian single-season occupancy model indicated that two environmental gradients, upstream drainage area and stream drying, influenced the probability of occurrence for multiple species of stream-breeding plethodontids. Further, species varied in their responses to these gradients. A second model was used to ask whether asymmetric interactions also influenced occurrence for three species of brook salamanders (Genus Eurycea). More specifically, the model tested whether the southern two-lined salamander (E. cirrigera) might act as the dominant predator and or competitor to either the three-lined (E. guttolineata) or dwarf (E. quadridigitata) salamanders. The results of this second model suggested that environmental gradients likely work in tandem with negative interactions to shape the distribution of E. guttolienata within the Gulf Coastal Plain. Like hierarchical occupancy models, genetic tools are also shedding light on complex relationships among and within species of lungless salamanders. This research investigated phylogeographic patterns within a wide-ranging species of plethodontid, the spotted dusky salamander (Desmognathus conanti). Sequence data revealed that there were geographically discrete, deeply divergent mitochondrial lineages within D. conanti which may be the result of isolation brought about by fluctuating sea levels during the late Miocene through the Pleistocene. Data from six rapidly mutating microsatellite markers indicated that there had been recent gene flow across some of these lineages in the southern Gulf Coastal Plain. However, these data also suggest that a northern lineage may have remained distinct. The relationships described and occurrence probabilities estimated by the aforementioned models, in combination with conclusions from analyses of genetic data, improve our ability to conserve regional plethodontid biodiversity within this unique physiographic province.

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