Experimental Taxonomy of Weissia controversa and W. sharpii (Musci: Pottiaceae)

Weissia sharpii Anders. & Lemmon is a recently described species endemic to the Southern Appalachian-Ozarkian region. It was distinguished from the more widespread species, W. controversa Hedw., on the basis of its diploid gametophytes, restricted habitat in cedar glades, and several morphological features of the gametophytes. An experiment was performed in which two populations each of W. sharpii and W. controversa were grown reciprocally on soil from each other's native habitats, and twelve morphological characters were measured. Soil type had virtually no effect on the expression of any of the characters. An analysis of variance indicates that the species differ significantly in leaf length-width ratio, upper leaf width, and in the width of the gap between involuted leaf margins. These morphological discontinuities, combined with differences in chro- mosome number and ecology, indicate that W. sharpii and W. controversa should be treated as separate species. Weissia controversa exhibited a greater degree of variation between populations than did W. sharpii when both were grown experimentally. This is in agreement with the relative variability of W. controversa in nature. Experimental studies on the plasticity of morphological characters in mosses and liverworts are reviewed. Weissia Hedw. is one of about sixty-five gen- era in the moss family, Pottiaceae. In their checklist of North American mosses, Crum et al. (1973) credited eight species of Weissia as occurring on this continent, but only one, W.