Molecular Taxonomy of Red Algae

Molecular taxonomy has transformed our understanding of red algal diversity by integrating DNA-based evidence with traditional morphology. Whereas classical classification relied on reproductive and vegetative traits, modern approaches employ mitochondrial, plastid and nuclear gene sequences to resolve species boundaries, infer phylogenetic relationships and estimate divergence times. Key markers include the mitochondrial cytochrome c oxidase subunit I fragment (COI-5P), plastid ribulose-1,5-bisphosphate carboxylase/oxygenase large subunit (rbcL) and chloroplast psbA, as well as nuclear ribosomal subunits (SSU, LSU) and protein-coding genes (e.g. EF2, psaA). Multilocus concatenated datasets, relaxed molecular clocks and coalescent-based delimitation methods now permit robust genus- and species-level inference, even in taxa lacking distinctive morphology. These tools have revealed cryptic lineages, redefined generic limits, and provided temporal frameworks for the evolution of Florideophyceae over nearly a billion years. Such insights underpin biodiversity inventories, inform conservation of habitat-forming corallines and turf algae, and facilitate the sustainable exploitation of commercially important taxa used for agar, carrageenan and other bioproducts.

Research from Nature Portfolio

Recent studies using a seven-gene concatenated alignment and relaxed-clock models have established a detailed timeline for florideophyte diversification, demonstrating deep splits among major subclasses and correlating morphological innovations—such as elaborate carposporophyte stages—with key geological intervals. In parallel, complete mitochondrial genomes obtained from archival type specimens of agar-producing genera have provided high-resolution gene synteny and sequence data. This work has clarified genus- and species-level boundaries, led to the transfer of mis-assigned taxa, and illustrated the power of mitogenome sequencing of type material to stabilise nomenclature and enhance taxonomic resolution in morphologically simple red algae.

Molecular Taxonomy of Red Algae publication trend

The graph below shows the total number of articles in molecular taxonomy of red algae across all publications each year (not limited to Nature Index journals).

Technical terms

Molecular taxonomy: Classification of organisms using DNA sequence data rather than solely morphological traits.

DNA barcoding: Use of a standard genetic marker (e.g. COI-5P) to identify and delimit species.

Phylogenetic marker: A gene or genomic region chosen for its evolutionary signal to infer relationships among taxa.

Mitogenome: The complete mitochondrial genome sequence, used for high-resolution phylogenetic analyses.

Relaxed molecular clock: A method that allows substitution rates to vary among branches when estimating divergence times.

Multilocus concatenation: The joint analysis of multiple gene sequences combined into a single dataset to improve phylogenetic support.

References

1. Genetic Diversity and Phylogeography of a Turf-Forming Cosmopolitan Marine Alga, Gelidium crinale (Gelidiales, Rhodo-Phyta). International Journal of Molecular Sciences (2023).
2. A New Species from the Canary Islands Increases the Diversity of the Red Algal Genus Pterocladiella in the Northeastern Atlantic. Plants (2023).
3. Divergence time estimates and the evolution of major lineages in the florideophyte red algae. Scientific Reports (2016).
4. Mitogenomes from type specimens, a genotyping tool for morphologically simple species: ten genomes of agar-producing red algae. Scientific Reports (2016).