Blechnaceae

Blechnaceae is a family of ferns, with a cosmopolitan distribution. Its status as a family and the number of genera included have both varied considerably. The influential Pteridophyte Phylogeny Group in their 2016 classification accept 24 genera. Most are ground dwelling, some are climbers, such as Stenochlaena. A characteristic feature of many species is that the young opening fronds are usually tinged with red. The family was created by Newman in 1844. In 2014, Christenhusz and Chase submerged it as subfamily Blechnoideae within the family Aspleniaceae. However, the PPG I classification of 2016 restored it to family status. Blechnaceae is a member of the eupolypods II clade (now the suborder Aspleniineae), in the order Polypodiales. It is related to other families in the clade as in the following cladogram: The number of genera accepted within Blechnaceae (or Blechnoideae when treated as a subfamily) has varied between authors. Christenhusz and Chase (2014), treating the group as a subfamily, describe the situation as follows: 'Blechnoideae comprise three major clades, one corresponding to Onoclea sensu lato, a second corresponding to Woodwardia, sister to all other species that can be treated as the single genus Blechnum. However, the subclade sister to the rest of Blechnum sensu lato contains the vining taxa Stenochlaena, Salpichlaena J.Sm. and a few non-vining Blechnum species with long-creeping rhizomes, which may have to be accepted at the generic level pending further studies. Brainea, Doodia, Pteridoblechnum and Sadleria belong to Blechnum sensu lato.' Perrie et al. (2014) retained the family rank and excluded Onoclea as a separate family, Onocleaceae, sister to Blechnaceae. They identified three major clades within the remaining Blechnaceae, which they labelled Woodwardia, super-Stenochlaena and super-Blechnum, with the latter two as sister groups. They did not consider Blechnum as monophyletic and recommended revision of intergeneric boundaries, resulting in seven genera. Gasper et al. (2016), independently of Christenhusz and Chase, examined the deeper relationships of the Blechnaceae, retaining its family status and excluding Onocleaceae, and allocated the three major clades of Perrie et al. (2014) to subfamilies: Woodwardioideae, Stenochlaenoideae and Blechnoideae. Their approach to the polyphyletic nature of Blechnum was to create a series of monophyletic segregate genera, resulting in 24 genera in total. The relationship between the three subfamilies was found to be as follows: In 2016, the Pteridophyte Phylogeny Group followed Gasper et al. (2016) in accepting 24 genera, grouped into three subfamilies. Of the approximately 265 species, the vast majority are attributed to Blechnum L., followed by Woodwardia Sm. and Stenochlaena J.Sm.. Other genera are largely monotypic.