Hybridization and Evolution in the Phlox pilosa Complex

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Abstract
Phlox pilosa ssp. pilosa and P. amoena ssp. amoena are interfertile species which are sympatric in the southeaster US. but remain spatially isolated because of different ecological tolerences. The rare establishment of composite populations results in hybridization. Phlox pilosa ssp. deamii and P. amoena ssp. lighthipei bridge the morphological and ecological hiatus between the aforemententioned species pair and have restricted ranges along the periphery of sympatric zone of the species pair. Certain products of natural hybridization between P. pilosa ssp. pilosa and P. amoena ssp. amoena are virtually identical to one or the other intermediate taxa. This evidence, coupled with the morphology, crossing and fertility relationships. and geography of the 4 taxa under consideration, strongly suggests that P. amoena ssp. lighthipei and P. pilosa ssp. deamii are products of hybridization and stabilization rather than intermediate steps in an evolutionary series.