The relationships of Papuasian cyatheaceae to new world tree ferns

Phylogenetic hypotheses about the Cyatheaceae have been based largely on either New World or Old World species. In this study we examine molecular data for species from both hemispheres. Chloroplast DNA restriction site variation has been compared among 23 species of Cyatheaceae from Papuasia and the Pacific and 61 species from the New World. Parsimony analysis of the variation documented supports the existence of three major clades, and reveals a correlation between phylogenetic relationship and biogeography. Species from the Neotropics appear derived with respect to those from the Paleotropics in the Alsophila clade; in this clade species from Papua New Guinea and Lord Howe Island are basal to those from the American tropics. A similar relationship is tentatively suggested for the Cyathea clade, where the sole Old World representative, (C. howeana) from Lord Howe Island, is basal to the remainder of the clade. This finding extends the worldwide distribution of the Cyathea clade across the Pacific. No clear correlation between phylogeny and biogeography of the Sphaeropteris clade was observed based on current data. These results suggest that additional sampling from other regions in the Old World tropics may further elucidate the evolutionary history of this group of plants.