9307211 Stein and Conant The tree ferns of the world, placed in the family Cyatheaceae, are a large group of ferns, ca. 500 species, with little variation in chromosome number. In this they are unusual for ferns, where polyploidy (chromosome complement doubling) and dysploidy (increase or decrease of individual chromosome pairs) mark many lineages. Possibly novel mechanisms of species divergence may operate in the tree ferns, such as diploid level speciation after hybridization. To explore such mechanisms, however, a phylogenetic framework for the tree ferns is required, in order to rationalize the choice of target or representative species for analysis. Drs. Stein and Conant are continuing their phylogenetic analyses of tree ferns, concentrating now on Old World species from the australasian regions. They are analyzing DNA mutations in chloroplast and nuclear genes to acquire new molecular data for phylogenetic reconstruction and to integrate with traditional morphological characters from fern taxonomy. %%% New molecular data from gene sequencing are revolutionizing our understanding of the evolutionary relationships of organisms. Work on Old World tree ferns will add data from both chloroplast and nuclear genes to traditional morphological features, to augment work on New World tree ferns. A robust phylogeny for this large group of plants will allow focused study on novel mechanisms of speciation and further analysis of t he direction of change in anatomical and ecological features of these ferns.
