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KINGDOM RHODOPHYTAE

This system roughly corresponds to some of the systems proposed by Cavalier-Smith (1981, 1998) in which the phycobillin-containing taxa are grouped together into a taxon that he called Billiphyta.  Similarly, Doweld (2001) united the glaucophytes and rhodophytes along with the cryptomonads as subkingdoms within a kingdom that he called Rhodymeniobiota.  Although the cryptophytes are troublesome with regard to their phylogenetic relationships, they clearly are the products of a secondary endosymbiosis, and, therefore, do not belong in this kingdom or supergroup of primary photosynthetic symbionts.  Patterson (1999) struggles to identify a synapomorphy for the red algae and concedes only that pit connections might be.  The relationships within the kingdom are even more problematic (Freshwater et al., 1994; and Garbary and Gabrielson, 1990), but are well on the way to being resolved by the system of Saunders and Hommersand (2004).  The "Cyanidiales" consistently emerge as a sister group to the other red algae (e.g. Gross et al. 2001; Ciniglia et al. 2004; Yoon et al. 2002; Muller et al. 2001; Saunders and Hommersand 2004).  Thus, I have followed the system of Saunders and Hommersand (2004) and set them apart as a distinct phylum.  The inclusion of the Glaucophyta into this kingdom is quite tentative and harkens back to the systems of Cavalier-Smith (1981, 1998) and Doweld (2001).  I include them here as a third phylum of primary photosynthetic endosymbionts with phycobillins as a phylum of incertae sedis.

Concepts and Terms for the Rhodophytae

A more complete taxonomy (to the ordinal level) of the Kingdom Rhodophytae.