Breaking the Mississippi River Barrier: Range Extensions of Faxonius palmeri Subspecies and Overlap with Rare Crayfish Species in Louisiana

Stream community surveys from 2008 to 2015 in the central Louisiana river basins (Red, Calcasieu, Vermillion-Teche, Mermentau, Ouachita, and Atchafalaya rivers) have resulted in new distributional data for 2 subspecies of Faxonius palmeri (Lowland Painted Crayfish). We also report unidentified Faxonius specimens appearing in streams of the northern Calcasieu River basin as well as a stream crossing the Mermentau-Calcaiseu River basin boundary, which warrant further investigation as to their identity. We determined that F. palmeri cannot be assumed to be separated along basin and river boundaries, and that the Mississippi River is probably not a biogeographic barrier for F. p. palmeri. We believe further species overlaps caused by range expansions of F. palmeri subspecies with endemic species of state conservation interest are likely.