Molecular phylogeny of the subfamily Bostrychioideae (Ceramiales, Rhodophyta): subsuming Stictosiphonia and highlighting polyphyly in species of Bostrychia

The Subfamily Bostrychioideae (Rhodomelaceae, Ceramiales) presently consists of two genera and about 17 species. Generic distinction within the subfamily is based on the number of tier cells (the results of transversely dividing pericentral cells) per axial cell, with two tier cells designating the genus Bostrychia and more than two characterising Stictosiphonia. Phylogenetic analysis of all but two species of this Subfamily based on DNA sequences from the nuclear-encoded 26S ribosomal RNA gene and plastid-encoded rbcL gene shows that this generic split is not supported. Our data Suggest that the subfamily may be split into two sections based on one or mother type of attachment Structure, as first proposed by Erika Post, but we propose that all species be returned to the genus Bostrychia due to as yet not fully resolved or Supported phylogeny. We also recommend that Bostrychia tenella ssp. flagellifera be returned to B. flagellifera because it does not group with B. tenella samples and shows a diagnostic synapomorphy (branching interval). Our data additionally show that many Currently circumscribed Species are not monophyletic. Even when B. tenuissima is regarded as synonymous with B. simpliciuscula, due to sequence identity, the resulting amalgamated species is still polyphyletic when Populations from broad geographic regions are analysed. Another possible polyphyletic species is B. calliptera. The clade containing cladohaptera (specialized attachment organs) is taxonomically unresolved but contains a heavily corticated species (B. pilulifera), a parasite (Bostry-chiocolax australis), pins several lineages in the Bostrychia radicanslB. moritziana Species complex thin are morphologically very similar.