DEFINING THE MAJOR LINEAGES OF RED ALGAE (RHODOPHYTA)¹

TLDR

Previous phylogenetic studies of the Rhodophyta have outlined a general framework for red algal evolution, yet a comprehensive analysis with broad taxon sampling is still needed to define the major lineages. The study aimed to identify the major clades of Rhodophyta by generating a robust phylogeny. The authors sequenced 48 PSI P700 chl a apoprotein A1 and rbc L coding regions and also analyzed smaller datasets comprising seven proteins or nine genes to resolve inter‑clade relationships. The resulting tree defined seven well‑supported lineages, including Cyanidiales as the earliest diverging group, and led to the proposal of two new subphyla (Cyanidiophytina and Rhodophytina) with six classes, as well as the description of a new order Rhodellales and family Rhodellaceae.

Abstract

Previous phylogenetic studies of the Rhodophyta have provided a framework for understanding red algal phylogeny, but there still exists the need for a comprehensive analysis using a broad sampling of taxa and sufficient phylogenetic information to clearly define the major lineages. In this study, we determined 48 sequences of the PSI P700 chl a apoprotein A1 ( psa A) and rbc L coding regions and established a robust red algal phylogeny to identify the major clades. The tree included most of the lineages of the Bangiophyceae (25 genera, 48 taxa). Seven well‐supported lineages were identified with this analysis with the Cyanidiales having the earliest divergence and being distinct from the remaining taxa; i.e. the Porphyridiales 1–3, Bangiales, Florideophyceae, and Compsopogonales. We also analyzed data sets with fewer taxa but using seven proteins or the DNA sequence from nine genes to resolve inter‐clade relationships. Based on all of these analyses, we propose that the Rhodophyta contains two new subphyla, the Cyanidiophytina with a single class, the Cyanidiophyceae, and the Rhodophytina with six classes, the Bangiophyceae, Compsopogonophyceae, Florideophyceae, Porphyridiophyceae classis nov . (which contains Porphyridium, Flintiella , and Erythrolobus ), Rhodellophyceae, and Stylonematophyceae classis nov . (which contains Stylonema, Bangiopsis, Chroodactylon, Chroothece, Purpureofilum, Rhodosorus, Rhodospora , and Rufusia ). We also describe a new order, Rhodellales, and a new family, Rhodellaceae (with Rhodella, Dixoniella , and Glaucosphaera ).