Using modern technologies such as determination of chromosome numbers, electrophoresis of enzyme variants, and scanning electron microscopy of minute morphological features, it has been possible to explicate patterns of hybrid speciation in ferns quite accurately. We know comparatively little, however, about the ancestry of the basic, non-hybrid-derived species. By studying members of the Polypodium vulgare complex, a group of about twelve species of temperate ferns, the proposed research will develop and test hypotheses about the systematics of basic diploid species. Comprehensive data bases will be accumulated on morphological features, biogeography, chromosome constitution, enzyme variability, and chloroplast DNA mutations. These data bases will provide the basis for a detailed exploration of the relationships among these species and should enable the analysis of Polypodium species to be extended into the tropical ecosystems. Through these studies we should gain insights on how the diversity in this relatively unexplored part of the world has contributed to the origin of our temperate flora. Thus, with the completion of the proposed research, we should have a modern synthesis of information on the primary and secondary speciation pathways in temperate Polypodium. By applying this model, modes and mechanisms that characterize patterns of diversity may be generalized for understanding the systematics of fern species and perhaps for a variety of other temperate plant groups.
