Multispecies assemblages of Appalachian desmognathans have long intrigued ecologists seeking to understand the structure of ecological communities. Body size and life history in this group correlate with the moisture gradient from stream to forest, with large species being more aquatic and progressively smaller ones being ever more terrestrial. Since the work of N.G. Hairston, Sr. in the early 1980s, the prevailing hypothesis has been that predation and competition among desmognathans themselves have been the driving processes in the development and maintenance of the spatial organization along stream sides, with large, aggressive species forcing smaller ones to occupy less favorable terrestrial niches. Decades of research have confirmed that biotic interactions are important. However, evidence from recent studies has not agreed with the idea that biotic interactions are primary. Herein, I have concluded that the prevailing hypothesis fails to reconcile the currently available data. I have presented an alternative hypothesis that an abiotic factor, specifically the relative abundance of water, has been the primary force driving adaptation of species of Desmognathus longitudinally along moisture gradients by way of stream headwaters. Interspecific interactions, though important aspects of the current ecology of these species, are not the underlying drivers of spatial organization along the moisture gradient. I have further generated specific predictions that will enable this hypothesis to be tested.