GENE FLOW IN THE RED-EARED SLIDER TURTLE (TRACHEMYS SCRIPTA ELEGANS) ALONG THE 
MISSISSIPPI AND ILLINOIS RIVERS.

James T. Lamer1, Michael A. Romano1, Richard V. Anderson1, John K. Tucker2. 1
Western Illinois University, Dept. of Biological Sciences, Macomb, IL  61455, 
2Illinois Natural History Survey, 1850 Montclair Ave, Brighton, IL  62012
      
T. scripta elegans is a an aquatic turtle species that inhabits a large portion 
of the Mississippi and Illinois Rivers, with well established populations 
utilizing sloughs and backwaters along its length.  Little is known on the 
effect large river systems play in the maintenance or possible hindrance of gene 
flow between potential interbreeding populations of this turtle.  In addition to 
the fluctuating current and variable water levels imposed by a riverine model, 
various structures such as dams and closing structures serve as potential 
obstacles.  A series of 14 T. scripta populations separated by distances ranging 
from 1-240 km were analyzed via starch gel allozyme electrophoresis.  It is 
shown that northern populations tend to have a lower percentage of 
heterozygosity to that compared to more southern populations.  One population, 
in particular, separated by Lock and Dam 19 on the upstream side of the 
Mississippi River, exhibited a marked deficit of H= .015 compared to that of the 
farthest southern population near Lock and Dam 26 of the same river with a 
gradual trend revealed moving downstream.  In addition, high FST values between 
proximal populations lean towards a maintenance of intrapopulational gamete 
exchange and conservation of large populations sizes in contrast to long-range, 
over-water, energy expenditures in the pursuit of gene flow with neighboring 
populations.
      
Keywords:  Trachemys scripta elegans, slider turtles, electrophoresis, allozyme 
variation, heterozygosity, gene flow