Systematics and Evolution of Polyploid Mosses

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Recently Drs. Wyatt and Stoneburner have provided the first molecular evidence for the probable hybrid origin of a natural species of moss, Plagiomnium medium. Using methods of isozyme analysis, widely employed in studies of flowering plants but only recently adapted to mosses, these scientists found protein composition in the moss to reflect additive components of two presumed parental species in the northern United States. The hybrid has double the number of chromosomes found in the two parents, and is fully fertile. This mechanism of species formation, by hybridization followed by chromosome doubling, has been amply documented in flowering plants, but not in mosses heretofore. Drs. Wyatt and Stoneburner will continue to sample more populations of these moss species and will extend the project to analyses of additional presumptive cases, where known chromosome counts suggest a probable hybrid origin. In the laboratory the investigators will attempt to cross-fertilize the presumptive parents in order to duplicate experimentally the hybrid species. Despite differences in the basic biology of mosses, with their dominant haploid life-cycle, this new work demonstrates fundamental similarity in a mechanism of evolution operating in all other land plants.