Phylogenetics, Biogeography, and Classification of the Woodwardioid Ferns (Blechnaceae)

Abstract

The woodwardioid ferns comprise fourteen species distributed among three genera of the Blechnaceae: Anchistea C. Presl, Lorinseria C. Presl, and Woodwardia Sm. The former two genera are monotypic and are confined to eastern North America, while the twelve species of the latter genus are disjunctly distributed throughout the warm temperate and subtropical regions of the northern hemisphere in a classic Arcto-Tertiary distribution pattern. Phylogenetic analyses based on characters derived from morphology and three molecular markers (rbcL,rps4, and rps4-trnS spacer) demonstrate that this group is monophyletic and is sister to the remainder of the Blechnaceae. Within the group, Woodwardia and Anchistea are sister taxa. A comparison of the phylogenetic results with known fossil history suggests that the group first arose sometime in the late Cretaceous in North America at high latitudes. Diversification of the major lineages of the group was complete by the Paleocene, with the lineages subsequently spreading southward into North America and westward into Asia, ultimately reaching Europe by the Miocene. The recent evolutionary history of the group has been characterized by extensive extinction and subsequent vicariance. We evaluate and discuss various hypotheses of relationship and character evolution proposed in the literature, and present a new classification for the group.