Abstract
The Blechnaceae is one of the most speciose fern families in New Zealand, with two genera represented: Blechnum and Doodia . We se‐quenced the chloroplast trn L‐ trn F locus for all of the Blechnaceae species indigenous to New Zealand, plus several non‐indigenous species. Although deeper relationships were not well resolved by phylogenetic analyses of these DNA sequences, several groupings of species were consistently recovered. Some of these relationships have been previously suspected on the basis of morphological similarity and/or hybridisation (e.g., the B. procerum group), and are consistent with variation in base chromosome numbers, but others were unexpected (e.g., the relationship of B. fluviatile and B. vulcanicum ). The species of Doodia sampled here were found to be monophyletic, and were nested within a paraphyletic Blechnum . Infraspecific variation in the trn L‐ trn F locus was detected within six New Zealand species, and may prove useful for future phylogeographic and taxonomic studies.