PHYLOGENETIC IMPLICATIONS OF CHLOROPLAST DNA VARIATION IN THE CYATHEACEAE .1.

Restriction site maps of the chloroplast DNA of four tree ferns (Alsop hila bryophila, Cyathea furfuracea, Sphaeropteris cooperi, and Lophoso ria quadripinnata) have been constructed using four enzymes. Genome si zes were estimated as ranging from 161.8 kilobases for L. quadripinnat a to 179.2 kilobases for C. furfuracea, the largest sizes thus far rep orted for ferns. Evolutionary relationships of 23 species of Cyatheace ae were assessed by comparative chloroplast DNA restriction site mappi ng. A total of 67 restriction site mutations, 58 of which were phyloge netically informative, was detected using 20 restriction enzymes. Phyl ogenetic analyses of restriction site mutations were carried out using both Wagner and Dollo parsimony and the resulting monophyletic groups were evaluated by bootstrapping. The data show strong support for thr ee major evolutionary lineages within the family: the ''Alsophila clad e,'' the ''Cyathea clade,'' and the ''Sphaeropteris clade.'' The ''Als ophila clade'' appears to be the most basal group in the family wherea s the ''Cyathea'' and ''Sphaeropteris clades'' are derived sister grou ps. Comparison of these results to the three modem classification syst ems for the family demonstrates that our findings are most consistent with the system of Lellinger.