Phylogenetic Relationships of Dennstaedtioid Ferns Based on DNA Sequence Analysis

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9307091 Wolf Determining evolutionary relationships among organisms is a major goal of systematists; phylogenies provide the necessary historical framework for studies of evolutionary processes, biogeographic dispersal and migration, and coevolution with symbionts and other ecological associates. Recently, DNA sequencing has provided valuable new data for phylogenetic analysis of plants, especially the flowering plants. Historically, ferns have been the subject of major taxonomic confusion, particularly at upper taxonomic ranks (families and orders), and a wide variety of classifications and hypothetical phylogenies exists for this group of ca. 10,000 species. This confusion results in part from a lack of morphological features that are both variable in their expression or form species to species but coherent enough to be homologous, that is, similar and comparable across numerous different species and genera. DNA sequence data are ideal characters for both reasons: variable among taxa but comparable across all of them, at least for functionally important genes. Dr. Paul Wolf of Utah State University is sequencing DNA from the chloroplast photosynthetic gene for numerous fern species allied in the "dennstaedtioid" group, in order to reconstruct their phylogeny under the working assumption that mutational differences track the divergence of species through time. %%% An independent molecular set of data will provide a valuable tool for assessing the origins of various fern groups as well as for examining patterns of morphological and chromosomal variation. The dennstaedtioid ferns constitute a major component of the leptosporangiate or "higher" ferns, and the data from this study will ultimately be combined with results from other laboratories working on DNA sequencing in ferns to provide a phylogenetic framework for all major fern lineages.