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Submitted on: 03 September 2007.
Revised on: 09 December 2007.
Accepted on: 05 January 2008.
___________________AMERICAN NATURALIST---UNIV CHICAGO PRESS
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Submitted on: 18 October 2010.
Revised on: 21 December 2010.
Accepted on: 09 January 2011.
___________________AMERICAN NATURALIST---UNIV CHICAGO PRESS
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Submitted on: 29 January 1998.
Revised on: 16 March 1998.
Accepted on: 06 April 1998.
___________________AMERICAN NATURALIST---UNIV CHICAGO PRESS