THE ORIGIN OF P. POLIONOTUS

As hypothesized by Lee R. Dice (1940) and W. Frank Blair (1950)

Stage 1. Incipient P. maniculatus originated in southwestern North America during Sangamon lnterglacial or earlier from an ancestral P. leucopus-allied population. Sea levels were higher than at present. Florida was insular, and the Gulf and southeastern Atlantic coastline were well inland from the present coast.

Stage 2. During the Wisconsin Glaciation (80,000 - 205,000 ybp) sea levels were lower than at present, expanding the southeastern coastline well beyond that of today. Range of P. maniculatus extended eastward along the southeastern coastal plain into Florida. The eastward flank represents incipient P. polionotus.

Stage 3. As sea levels rose at end of the Wisconsin Glaciation and the Mississippi River Delta developed from glacial melt runoff, P. polionotus along the eastern Gulf Coast became physically isolated from the parent P. maniculatus populations of the southwest. The Texas race of P. maniculatus, P. m. pallescens, remains morphologically and ecologically similar to P. polionotus.

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